2409.26b,60
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FOREST SERVICE HANDBOOK
PORTLAND, OREGON
2409.26b - REFORESTATION HANDBOOK
R-6 Amendment No. 2409.26b-92-2
Effective February 7, 1992
POSTING NOTICE. Amendments to this handbook are numbered consecutively.
Check the last transmittal sheet received for this handbook to see that the above
amendment number is in sequence. If not, obtain intervening amendment(s) at
once from the Information Center. Do not post this amendment until the missing
one(s) is received and posted. After posting, place the transmittal at the front of the
title and retain until the first transmittal of the next calendar year is received.
The last amendment to this handbook was 2409.26b-92-1 (2409.26b,30).
Document Name
Superseded New
(Number of Sheets)
60
2409.26b,60
29
29
Digest:
This is a Technical Amendment to change the Document Name. CONTENT HAS
NOT BEEN CHANGED.
JOHN F. BUTRUILLE
Regional Forester
R-6 AMENDMENT 2409.26b-92-2
EFFECTIVE 2/7/92
2409.26b,60
Page 2 of 29
FSH 2409.26b - REFORESTATION HANDBOOK
R-6 AMENDMENT 2409.26b-92-2
EFFECTIVE 2/7/92
CHAPTER 60 - SEEDLINGS
60
SEEDLINGS
60.1
Critical Dates For Reforestation Program Coordination
61
SEED
62
ORDERING TREE SEEDLINGS
62.1
62.11
62.2
62.21
62.22
62.23
Sowing Requests
SOWREQ Requires the Following Information
Selection of Stock
Species Selection
Type of Planting Stock
Matching Stock and Site
63
NURSERY
63.1
63.2
63.21
63.22
63.3
63.31
63.32
63.33
63.34
Nursery Visits
Seedling Inventories
1-0 Inventory
2-0 Inventory
Nursery Grading Standards Specifications
Caliper and Height
Root System
Stem
Vigor
64
LIFTING REQUESTS (INVORD)
65
CARE AND HANDLING OF SEEDLINGS
65.1
65.2
65.3
65.31
65.32
65.33
65.34
65.35
65.4
65.41
65.42
Lifting
Grading, Bundling, and Packing
General Requirements For Seedlings After Lifting
Dormancy
Temperature
Humidity
Root Exposure to Light
Exposure to Toxic Substances.
Freezer Storage
Seedling Condition Necessary for Freezer Storage
Freezer Storage Guidelines
R-6 AMENDMENT 2409.26b-92-2
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65.43
65.44
65.45
65.46
Post-thaw Options
Handling of Frozen Seedlings
Transportation of Frozen Seedlings
Freezer Storage References
66
SHIPPING SEEDLINGS FROM NURSERIES
67
RESPONSIBILITIES OF DISTRICT ON RECEIPT OF TREE SEEDLINGS
67.1
67.2
67.3
67.4
67.5
Stock Condition
Temperature of Delivered Stock
Assessment of Violation Other Than Temperatures
Bareroot Stock
Container Stock
68
LOCAL STORAGE AND SHIPMENT TO THE FIELD
68.1
68.11
68.2
68.21
68.22
68.3
68.4
68.5
Storage
Tree Storage Standards
Shipment to Planting Site
Acclimatization
Transport of Seedlings
Storage of Seedlings at Planting Site
Root Pruning in the Field
Care of Seedlings By the Planters
69
SPECIAL CONSIDERATIONS FOR CARING FOR PLANTING STOCK
69.1
69.11
69.12
69.13
69.2
69.21
69.22
69.23
Suspension of Planting
Soil Moisture
Atmospheric Moisture Demand
Frost and Snow
Special Packaging of Seedlings
Jelly Rolling
Root Dipping
Insulated Planting Bags
APPENDIX
A REFERENCE LIST
B JELLY-ROLLING SEEDLINGS
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EFFECTIVE 2/7/92
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60 - SEEDLINGS. The purpose of this chapter is to provide an overview of the
seedling production and care process from tree seed inventory planning and nursery
sowing request formulation to planting the seedling. Cross references to the Seed
Handbook (FSH 2409.26f R-6) are provided for language pertaining to seed and
cones.
60.1 - Critical Dates for Reforestation Program Coordination. The following table
contains the schedule of paperwork events which must be completed to efficiently
conduct the business of reforestation. These dates will not be repeated elsewhere in
this handbook.
Reforestation Document Due Dates:
Item
Seed
Inventory
Review
(Excess/Unusable)
Excess Seedling
Report
Seed Disposal
List (Unserv.)
Seed/Cone
Procurement Plan
Review
Approval
Sowing Schedules
Fall 2/
Spring
Seedling
Inventory 4/
Lifting Request
Fall
Spring
Excess Seedling
List
Lifting
Confirmation
Fall
Spring
Destination
Nursery
Origin
S.O.
R.O.
Nursery
RO 1/
6/15
-
6/15
9/30
9/30
Nursery
-
12/1
-
RO
4/1
-
4/1
SO
-
-
7/10
Nursery
RO
8/1
7/20
-
8/1
SO
RO 3/
SO
RO 3/
Nursery
8/10
1/10
-
8/1
11/20
9/1
8/1
8/10
11/20
12/31
9/1
SO
SO
SO
-
-
9/1
11/15
11/15
Nursery
12/1
RO distribute to potential customers by 12/15
-
Nursery
Nursery
-
9/10
12/10
-
R-6 AMENDMENT 2409.26b-92-2
EFFECTIVE 2/7/92
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1/Review
2/Include container and transplants, all producers.
3/Approval
4/All producers, all age classes.
61 - SEED. Information pertaining to collection, extraction, identification, care, and
shipping of tree seed and cones is contained in FSH 2409.26 R-6.
62 - ORDERING TREE SEEDLINGS. Tree seedlings, as well as any product
Forests wish to have nurseries produce, for example, bitterbrush, willow,
elderberry, are ordered through the use of the electronic database systems SOWREQ and INVORD. This system will be used for requesting sowing seedlings
to all nurseries; federal and private. It is the responsibility of the Forest Supervisor
to ensure the use of the most current update of the SOWREQ and INVORD
databases.
These database/reporting systems are available in the Data General electronic mail
system, so no paper copies are needed until completed requests are printed out in
the Regional Office. Detailed instructions on the use of these databases are
generated, maintained, and stored at the J. Herbert Stone Nursery. Questions
regarding the use of these systems should be directed to the System Operator at the
J. Herbert Stone Nursery.
Seedling size specifications necessary for ordering are found in subsection 63.31.
62.1 - Sowing Requests. The seedling production request originates at the Ranger
District through the use of the SOWREQ database. The Forest Supervisor
combines the Districts' plans into a Forest plan, also in SOWREQ. The consolidated
datafile is electronically sent to the Regional Office, and each Nursery receives it's
own individual datafile. Refer to Table in subsection 60.1 for due dates.
Requests from Forests will be consolidated by the Regional Office to be used as a
Nursery sowing schedule.
The approved summarized Nursery Sowing request will be sent to each Nursery
and Forest Supervisor.
The distribution of the approved nursery sowing request will authorize the
shipment of the tree seed to the appropriate nursery and the reimbursement
voucher for seed cost. Seed cost will be paid when seed is withdrawn from storage
and not included in seedling cost.
No seed will be disbursed from storage without prior approval of the Forest
Supervisor of the Forest of seed source.
62.11 - SOWREQ Requires the Following Information.
1. Species
R-6 AMENDMENT 2409.26b-92-2
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2. Seed lots to be sown.
3. Number of seedlings.
4. Caliper of seedling.
5. Height of seedling.
6. Shoot-root ratio.
7. Special instruction (top pruning, and so forth).
8. Nursery to be grown at.
9. Forest Service Nursery or contract grower.
10. Seed bank location.
11. Seed bank identification code.
12. Sowing year (calendar year).
13. Production age (seedling age at time of lifting).
14. Production year (fiscal year to be lifted).
62.2 - Selection of Stock. Classifying the planting site environment is important, in
the long term, for selecting species and seed source and, in the short term, for
determining morphological and physiological seedling characteristics. Using the
correct species and seed source will ensure that seedlings are adapted to infrequent
climatic extremes or diseases which could affect plantation performance in the
future but go unnoticed during establishment.
Seedlings with the correct
morphological and physiological characteristics are better adapted to meet initial
threats to survival and optimal growth, such as animals, lodging of cured
vegetation, or heavy brush competition.
MORPHOLOGICAL TABLE 1/
SITE
CONDITION
SPECIFICATION
Douglas-fir
Height Caliper T/R
cm
mm
Droughty 2/
15-25
5-6
1.0-1.5
Brush
30-40
4-6
1.0-2.0
Deer-Elk
30-40
4-6
1.0-2.0
20-30
5-6
1.0-2.0
Steep2/
Other(NurStd > 15
>4
1.0-3.0
SPECIES
Noble Fir
Height Caliper
cm
mm
10-15
5-6
20-25
4-6
20-25
4-6
15-20
5-6
> 15
>4
T/R
1.0-1.5
1.0-2.0
1.0-2.0
1.0-2.0
1.0-3.0
Ponderosa Pine
HT
CAL T/R
CM
MM RATIO
15-30 5-6
1.0-1.5
20-35 4-6
1.0-2.0
20-35 4-6
1.0-2.0
15-30 5-6
1.0-2.0
>15
>4
1.0-3.0
R-6 AMENDMENT 2409.26b-92-2
EFFECTIVE 2/7/92
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Page 7 of 29
1/Exhibit derived from Mt Baker-Snoqualmie NF, White River RD Planting Stock
Size Standards.
2/Low Nursery Density - 17-21 live seedlings/square feet.
HEIGHT - Short top reduces transpirational surface.
Tall top requires larger caliper.
Tall top is a liability on a steep slope.
CALIPER- 5-6 mm for large root system. Stout caliper usually assures matching
root system.
Up to 6 mm for tall tops.
GREATER THAN 6 mm DIFFICULT FOR NURSERY MANAGER.
Greater than 6 mm on steep slopes does not provide enough additional
resistance to be economically feasible.
T/R
- Ratio lower than 1.0 is too low.
Ratio 1.0-2.0 good for most problem area.
Up to 3.0 good for normal sites.
Ratio 1.0-2.0 good for dry sites.
We should not be too particular with the Nursery Managers because the range of
characteristics we are working with is quite narrow.
62.21 - Species Selection. Each species will be best adapted to a given range of
environmental conditions. Proper species selection may require more than just
surveying native tree species and their relative frequency in the previous stand.
Some may be better adapted to the environments created by harvesting or other site
disturbances.
A generally accepted rule is that the seral or pioneer species will survive better and
grow faster on clearcuts and burned areas than the climax species.
Other site factors also are important in selecting species. Using certain species is
risky because of their vulnerability to insects and diseases.
Management objectives may influence preferred species to be grown for timber
production on certain sites or for recreational purposes, but species conversions
must be approached with caution.
62.22 - Type of Planting Stock. Size and type of planting stock is an important
controllable factor.
Assuming the stock is in good physiological condition, then stem caliper is more
important than height. Stock with 4-6 mm caliper and root systems 25-30 cm (10"12") long will out-perform tall, spindly stock. In general, severe site on slopes with
south and west exposures will require a minimum caliper of 4 mm unless artificial
shade is provided at the stem groundline. Container grown and 1-0 stock should
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not be planted on harsh sites without shading. Small caliper seedlings are also very
suspectible to small animal damage.
Container grown stock is usually more expensive than bareroot and offers no
appreciable survival advantages under proper planting conditions on most sites.
However, container stock gives the program flexibility and is recommended for:
1. Planting high elevation sites that are difficult to access in the spring due to
snow plowing requirements. These sites can be planted early in the fall with
container stock. Container stock may also be used to extend planting season.
2. Planting extremely rocky sites where it is difficult to open a hole properly
for bareroot stock.
3. Planting areas where site preparation would be lost if the area had to wait
for bareroot stock to be produced. Container stock has the advantage in that it can
be ordered in January and shipped the next fall or the spring of the following year.
Container stock is often used to make up shortages from bareroot nurseries or first
year failures in the field.
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EFFECTIVE 2/7/92
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62.23 - Matching Stock and Site. A wide range of planting conditions exists on some
Forests or Ranger Districts. Close attention to the details can improve survival and
growth of planted trees. For these areas, prescribe for the most limiting condition
and use the stock everywhere. Nursery stock can be tailored to specific planting
sites by careful use of nursery cultural practices. Among the site conditions which
can be ameliorated by manipulation of stock characteristics are physical planting
difficulty, high transpiration demand, droughty soils, animal pressures, overtopping
vegetation, and topography.
In general, gentle north slopes have few problems amenable to morphological
solutions. Steep south slopes have many problems which may be ameliorated by
morphological solutions. South slopes have ravel, freeze-thaw, and heat. Animals
also visit south slopes first because these slopes are usually first to emerge from
snow and first to green up in the spring.
1.
Soil. Planting difficulty (rocks) may call for containerized trees.
Shallow soil may call for short bushy, fibrous root systems.
2.
Drought. Short stubby trees are needed to reduce transpirational
surfaces. Large caliper will also generally assure a good root system.
3.
Animals. This depends on the animal. Pressure from clipping animals
requires larger caliper. For browsing animals, prescribe a woody top with good
lateral branches. For cattle grazing, possibly a bareroot transplant or plug-1 is
best, particularly if trees cannot be protected.
4.
Overtopping vegetation. A large tree is needed here. It must be tall
enough to get above brush and have large caliper to resist rabbits. In the Coast
Range root systems can be small because moisture should not be a problem. In the
Cascades and on the east side root systems must also be large.
5.
South slopes. Generally, large caliper is needed to protect against
ravel, thick bark for heat resistance, and a bushy top to provide shade for the stem
and the ground line. Moisture demand will be high so an adequate root system is
essential.
63 - NURSERY. The intent of this section is to provide guidance to Forest
personnel in understanding the nursery's role and standards in the reforestation
process.
63.1 - Nursery Visits. Plans should be made to visit the nurseries where seedlings
are being grown at least on an annual basis so the client and nursery personnel
have a common understanding of specific needs and the capability of the nursery to
meet those needs. September or October is a good time to make these visits.
Annual visits will provide an opportunity to see the stock, which will aid clients in
discussing cultural treatments with the Nursery Manager for their stock, make
adjustments in future sowing or lifting requests, and establishment of all cull rules.
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This interaction between seedling users and producers is very important. Each
must respect the other's professional judgement.
63.2 - Seedling Inventories.
63.21 - 1-0 Inventory. The nurseries will prepare a 1-0 inventory for Forests
showing the quantity of seedlings by September 1 of each year. The 1-0 inventory
will be reported as a gross (all seedlings present) figure.
Forest will review 1-0 inventory.
63.22 - 2-0 Inventory. The nurseries will prepare a 2-0 and older inventory sending
copies electronically to the Regional Office and the Forests by September 1 of each
year. The inventory will include the height, caliper, shoot-root ratio measurements
and quantity. 2-0 inventories are net plantable seedlings.
63.3 - Nursery Grading Standards Specifications. These nursery standards are to
be used as guidelines. They are nursery goals and not cull rules. Cull rules
must be agreed upon in consultation between silviculturists and Nursery Managers
as referred to under 63.1, Nursery Visits.
63.31 - Caliper and Height.
SPECIES
Douglas-fir
AGE CLASS
2-0
1-1
1-0
Douglas-fir (East Side) 2-0
1-0
True Fir
2-0
3-0
2-1
Ponderosa Pine
2-0
1-0
Lodgepole Pine
2-0
Engelmann Spruce and 2-0
Western Red Cedar
3-0
Western Larch
2-0
1-0
Other Species
2-0
3-0
2-1
Bedhouse 1/
Douglas-fir
1-0
Douglas-fir (East Side) 1-0
True Fir
1-0
MINIMUM CALIPER
AT GROUND LEVEL
5/32" (4 mm)
5/32" (4 mm)
1/8" (3.5 mm)
5/32" (4 mm)
1/8" (3.5 mm)
5/32" (4 mm)
5/32" (4 mm)
5/32" (4 mm)
5/32" (4 mm)
1/8" (3.5 mm)
5/32" (4 mm)
5/32" (4 mm)
5/32" (4 mm)
5/32" (4 mm)
1/8" (3.5 mm)
1/8" (3.5 mm)
5/32" (4 mm)
5/32" (4 mm)
MINIMUM SHOOT
LENGTH TO TIP
OF TERMINAL BUD
6" (15 cm)
6" (15 cm)
4" (10 cm)
4" (10 cm)
4" (10 cm)
4" (10 cm)
6" (15 cm)
6" (15 cm)
6" (15 cm)
3" (7.5 cm)
4" (10 cm)
4" (10 cm)
6" (15 cm)
6" (15 cm)
4" (10 cm)
6" (15 cm)
6" (15 cm)
4" (10 cm)
1/8" (3 mm)
1/8" (3 mm)
1/8" (3 mm)
6" (15 cm)
4" (10 cm)
4" (10 cm)
R-6 AMENDMENT 2409.26b-92-2
EFFECTIVE 2/7/92
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1/Wind River Nursery only.
63.32 - Root System. Root pruning will be accomplished at 12 inches, unless
otherwise specified by the ordering unit. Point of reference for measuring root
length commences at the cotyledon scar. Planting stock shoot-root systems should
not exceed a 3:1 ratio. Planting stock root systems should have at least 1/3 to 1/2 of
the smaller feeder roots intact. When the tap root is split or severed 6 inches (15
cm) or less from the ground line, the seedling is considered a cull. Any seedling
exhibiting indications of root rot disease must be culled.
63.33 - Stem. When mechanical damage into the stem or root exceeds more than 33
percent of the stem and 3/4 inch (1.9 cm) in length, the seedling must be culled. All
gradeable seedlings must have at least one-third of the stem capable of
photosynthesis. Needle mottling, chlorotic needles, needle cast, disease, insects,
spindliness, mechanical damage, or other defects lessening the vigor and ability of a
seedling to survive and grow must be considered when establishing cull rules.
Seedlings infected with Botrytis cinerea will not be culled unless requested by the
receiving unit.
63.34 - Vigor. All grading of stock must be accomplished within an hour of the time
the stock is pulled from the seedling bed unless stock is stored in the precooler at
90 percent relative humidity and 1o-2oC (33o-36oF) temperature. The stock will be
given maximum attention to prevent deterioration of vigor by various desiccating
effects from time of lifting through planting. Pressure chambers will be employed to
determine plant moisture stress during lifting and packing operations, and to
trigger any subsequent mitigating actions to reduce the stress.
64 - LIFTING REQUESTS (INVORD). Utilizing the INVORD database, Ranger
Districts will prepare lifting requests and send them to the Forest Supervisor for
consolidation. The consolidated lifting requests will be sent directly to the nursery
producing the stock. The Forest is automatically allocated the trees that were
ordered sown providing they are on the inventory. Forests are not obligated to take
overages in one lot to make up for shortage in another lot. However, if the Forest
requests the overages, the Forest becomes financially obligated for these seedlings.
The Forests will send the lifting requests directly to comply with the dates in
subsection 60.1.
Lifting requests will include:
1. Species codes.
2. Root lengths.
3. Number of seedlings.
4. Tentative delivery date.
5. Packaging type.
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6. Packing material needed.
7. Other special treatments.
8. Accounting data for paying for the seedlings.
The Nursery will notify the Forest of lifting confirmation, agreement with the lifting
request, to comply with the dates listed in 60.1.
65 - CARE AND HANDLING OF SEEDLINGS. Of the factors that influence the
survival of planted seedlings, the greatest control is over care and handling. The
manner in which seedlings are handled will influence final results to a significant
degree.
All those connected with the planting program share the responsibility for
exercising extreme care in the lifting, pulling, sorting, packing, transporting,
storing, handling, and planting of seedlings.
65.1 - Lifting. The intent of this section is to help Forest personnel understand the
importance of proper timing and protection during harvesting of seedlings.
Lifting (loosening of seedlings in the soil) should be done during the period when
Root-Growth Capacity (RGC) peaks. Root-growth capacity of Douglas-fir seedlings
rises steadily from September to a peak during the period from January to March
and is followed by a rapid decline to the September level. Most temperate zone
species follow this general pattern. However, much variation may be present
among species or for different seed sources with species.
Seedlings lifted when completely dormant have higher resistance to damage or
stress imposed during handling.
Lifting window studies are necessary to best determine lifting dates for specific seed
sources. Once identified, lifting windows can be assumed to be relatively constant
for the specific nursery tested. Annual climatic variations may influence the
window, but generally not to any great degree. A word of caution for lifting window
study participants: Lifting window study outplantings for spring lift dates must
include storage periods comparable to those likely to be required for operational
outplantings.
Seedlings should be lifted within the established lifting windows for the particular
species and nursery. Seedling dormancy and RGC are physiological factors which
affect lifting windows. Though precise lifting windows are not known for all species
produced at all nurseries, Nursery Managers become familiar with the
requirements of specific seed sources. Field foresters should respect the Nursery
Managers' professional judgement on matters relating to lifting, if specific lifting
windows are not known.
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The best time to lift seedlings, within the window, is when Plant Moisture Stress
(PMS) is low. This occurs early in the morning, or when the weather is cool and
humid. These conditions also favor lifting because they minimize the potential
harmful rise in PMS during field handling.
To reduce mechanical damage, lifting should be restricted to occasions when the
ground is not frozen or the soil is not saturated. The degree of damage resulting
from lifting can be assessed by the number of stripped or broken roots.
Desiccation of seedlings during lifting can be reduced by protecting lifted seedlings
from direct exposure to the sun, reducing the time required to transfer lifted
seedlings to field containers, misting seedlings in the field immediately after lifting,
and limiting lifting operations to times the evaporatranspiration rates are low.
Tree seedling roots, especially the fine roots, can become desiccated rapidly when
exposed to air. Lifted seedlings should, therefore, be placed in a field container and
covered as soon as possible to prevent moisture loss.
Plant moisture stress of seedlings should generally not exceed -20 bars immediately
prior to lifting and should trend down shortly after pulling. Again, the professional
judgement of the Nursery Manager must be recognized, and mitigation efforts will
allow certain instances of lifting to continue in those infrequent instances when the
plant moisture stress does slightly exceed -20 bars. On days of high atmospheric
moisture demand, seedling pullers should follow closely behind the lifting machine.
A distinction should be drawn between desiccation of root surfaces and PMS. For
instance, short exposure of tender root surfaces to dry air may cause root damage
without a corresponding increase in PMS. Since root surfaces have no way of
controlling moisture loss as needles have, these cells can be killed quickly without a
corresponding increase in PMS. Conversely, PMS can increase dramatically in the
xylary plumbing of the plant without killing root or other cells when these cells are
not subject to evaporation. Therefore, root damage from drying may occur at low
PMS and not at high PMS.
Solar heating of tree seedlings in field containers can be rapid. Field containers
should, therefore, be hauled to the packing shed as soon as seedlings have been
lifted, and be placed in refrigerated storage as soon as they arrive from the field. If
there is a delay in storage it should not exceed 1 hour.
65.2 - Grading, Bundling, and Packing. Once the seedling is lifted, its condition can
change rapidly as a result of desiccation, molding, metabolic activity, or
developmental processes. Success in minimizing the deterioration of stored
seedlings depends primarily on controlling plant water content and temperature.
Prepacking cooling of seedlings can greatly minimize the deterioration as
temperature is a major contributing factor.
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EFFECTIVE 2/7/92
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Grading, bundling, and packing of seedlings should be done in a cool, humid
environment to protect the root system from desiccation. Space heaters, directed
toward the grading table, should not be used in the packing shed.
During the grading process, seedlings should be individually separated (singulated).
This allows for the culling of seedlings which may be damaged during the lifting
operation, and for the separation of the entangled root masses.
The time a seedling is on the grading table (belt) should be kept to a minimum
consistent with maintaining PMS at the 5 bar level.
Grading standards used for each seedling lot should be based on the local site need.
Such standards must be established by consultation between Nursery Managers
and field foresters, both at the Nursery and on the planting sites as time and travel
schedules permit.
Seedlings are often tied into bundles of a standard number, such as 50, which aids
in determining the number of seedlings per storage container and lot. CAUTION:
Bundling of seedlings may cause some damage to the seedlings if the bundles are
tied too tightly or when the bundling material is removed incorrectly.
Pruning of root systems should be done in a manner which minimizes the stripping
of roots, and provides a clean cut surface.
65.3 - General Requirements For Seedlings After Lifting. From the time seedlings
are lifted until they are outplanted, safeguards must be taken to control dormancy
temperature, humidity, root exposure to light, and exposure to toxic substances.
65.31 - Dormancy. Trees must be kept in a dormant state to prevent stress and loss
of vigor. Trees that have broken dormancy deteriorate rapidly even under the best
storage conditions. Survival and growth of outplanted trees decreases rapidly as
storage time increases for trees that have prematurely broken dormancy.
Trees break dormancy due to a change in their environment, such as heat. Root
growth and other physiological processes begin before bud burst is evident. Storage
temperatures must be low enough to prevent this activity.
Dormancy release is often shown by the softening and enlargement of buds, and the
upturning and/or elongation of terminal or lateral candles on seedlings stored
horizontally.
Root growth is not an indicator of dormancy release as root tips do not become
dormant. They simply stop growing when temperatures drop below approximately
35oF. (This is species dependant.) An occasional white root tip on stored seedlings
is not cause for alarm.
65.32 - Temperature.
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1. Heat. Respiration and micro-organism activities increase within tree
packages when temperature rises above 2oC (36oF). This physiological activity
raises temperatures even higher. Stored food (carbohydrate) reserves are depleted
at a fast rate.
2. Cold. Mechanical injury, such as broken twigs and roots, may be caused by
handling frozen trees. Frozen trees should be thawed slowly at temperatures below
10oC (50oF) and in an area protected from wind and direct sun. Thawing time will
vary depending on many factors, particularly packaging. A generally acceptable
range is 1-15 days.
3. Temperature Fluctuations. Significant temperature changes adversely
affect seedlings in transit and storage. Transpired water vapor condenses on inner
bag surfaces and collects on bag bottoms drying trees and forming a mold hazard.
65.33 - Humidity. Trees in storage have a limited water supply. Much of the tree's
ability to absorb moisture has been lost when roots were left in frozen soil and when
they were pruned at the nursery during lifting and prior to packaging.
High storage humidities are essential to prevent water loss from needles and roots.
If plant moisture stress measures six (6) or more, roots should be watered.
65.34 - Root Exposure to Light. The full effect of exposing seedling roots to direct or
diffused light is not known, but it is contrary to their natural environment. Tree
roots are normally shielded from light by soil. Light intensities and solar heating
are more serious at high elevations where atmospheric protection is less.
65.35 - Exposure to Toxic Substances. Substances, such as pesticides, petroleum
products, and chemicals are lethal to seedlings. Gas and oil for planting augers and
saws must not be transported in contact with seedlings. Also, seedlings should not
be stored with fruit as the production of ethylene gas also is detrimental to seedling
performance.
65.4 - Freezer Storage. Freezer storage (storage below 0oC) is an alternative to
storing seedlings at temperatures just above freezing. There are a number of
advantages to freezer storage including:
1. Storage time can be extended.
2. Storage molds are better controlled.
3. Respiration, loss of dry weight and loss of carbohydrate reserves are
reduced.
4. Dormancy release is delayed.
5. Winter losses in nursery and field are reduced.
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6. Earlier and more accurate inventories can be made.
7. Nursery workload is better balanced.
8. Shipping to early opening planting sites can occur.
Both containerized and bareroot seedlings may be stored frozen. Freezer storage is
appropriate for fall-lifted seedlings, winter-lifted seedlings, and early spring-lifted
seedlings, especially when the anticipated storage period is greater than 2 months.
65.41 - Seedling Condition Necessary for Freezer Storage. Prior to placement in
freezer storage, seedlings must be sufficiently dormant to withstand freezer storage
temperatures. Seedlings must be entering dormancy rather than exiting dormancy.
If seedlings are exiting dormancy, they will be less cold hardy and tissue can be
damaged by below-freezing temperatures. With increasing dormancy, the seedling
can withstand increasing amounts of cold without freezing the intracellular
contents.
Chilling requirements will be met in freezer storage; seedlings will be ready to grow
when warmed. Refrigerated storage must be used to keep product temperatures
(seedlings) below 35oF during and after thawing if seedlings are not planted
immediately. After thawing it is possible to maintain seedlings in refrigerated
storage for a considerable length of time without any expected deterioration.
Seedlings should be hardy to -5oC prior to freezer storage (Hee, 1987). Hardiness
and appropriate lift dates will vary from year to year, depending on frost hardiness
and chilling hours received.
Frost hardiness tests, as well as monitoring
accumulated chilling hours may be used to determine when seedlings can be lifted
and freezer stored.
65.42 - Freezer Storage Guidelines.
1. Freezer facilities.
(a) Temperature capability:
(1) Range: 26o-50oF (for freezer and cooler capability).
(2) Ability to regulate within 2oF.
(3) Air temperature off coils not more than 3o-5oF below minimum
temperature.
(4) Freezer set point: 28o-30oF
(5) Alarm points: 27oF, 31oF
(b) Humidity: Humidification is not necessary with freezer storage.
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(c) Types of systems:
(1) Direct Expansion (DX): With DX system, air off coils is below
thermostat setting, allowing for temperature variation throughout the
box. Inside bag temperatures will be more stable than ambient box
temperature, but monitoring inside bag temperatures must be done to
ensure that "warm spots" and "cold spots" fall within desired
temperature range.
(2) Glycol: With glycol system, air off coils will be the same
temperature as the thermostat temperature so that there is minimum
variation in temperatures within the box.
2. Freezing Procedure.
a. Temperature: CAUTION: Seedling temperature refers to the
inside bag temperature of the seedlings. It does not refer to the
ambient temperature of the cooler.
Bring seedling temperature down to 32o-34oF as quickly as possible
after packing, or when frost hardiness tests indicate that seedlings are
hardy to 28oF or below. Seedlings may be held at 32o-34oF for 4 weeks
to enhance cold hardiness. (Pre-cooling the freezer to 28oF is an
effective means of initially cooling down seedlings to 32o-34oF.)
Lower seedling temperature to 28o-30oF slowly by lowering ambient
1oF every 4 days. Hold seedlings at 28oF until thawing/shipping. Many
seedlings can be frozen at temperatures much lower than 28 oF, but
28oF is specified as minimum to prevent damage to seedlings or species
which are not fully dormant or are not as hardy.
b. Humidity:
commences.
Humidification should be turned off when freezing
c. Duration: Seedlings of some species (lodgepole pine, noble fir,
western hemlock, Douglas-fir, ponderosa pine) have been kept in freezer
storage for up to 6 months with no significant effects on survival or
growth. Most species can be effectively frozen for 6 months.
3. Packaging. Seedlings in frozen storage must be provided with an
adequate moisture barrier to prevent desiccation. Either polyethylene bags placed
in a packing box or a 3-ply polyethylene coating inner ply bag will provide adequate
moisture barriers. In either case, the bags must be sealed. If bags or boxes are
punctured during storage or transport, the opening should be mended and resealed.
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4. Seedling moisture. Seedlings should be moist, but not wet, prior to
frozen storage. Dipping roots in water prior to freezing is not recommended.
5. Packing materials. Use of packing materials, such as peat or vermiculite
around the roots is optional. Consistent benefit from using these materials has not
been demonstrated. Additional thawing time is required if additional materials are
placed around the roots.
6. Monitoring. Temperatures in the freezer (ambient and within bag, if
possible) should be monitored daily. A hygrothermograph or other monitoring
device should be used to continuously monitor and provide a record of temperatures.
Freezers should be equipped with an alarm which is activated when temperatures
rise above or fall below the set temperature.
7. Thawing Procedure.
a. Temperature:
(1)
Ambient:
>35oF (QUICK THAW):
Seedlings thawed at
temperatures >35oF will thaw relatively quickly. Bareroot seedlings
will thaw more quickly than extracted containerized seedlings (3-5 days
at 40o-50oF for former; 2-3 weeks at 40o-50oF for later). Thawing should
be accomplished under controlled and/or monitored conditions. It is
preferred that thawing be done in buildings where temperature
fluctuations are not sufficient to cause re-freezing at night and rethawing during the day. Seedlings should not be thawed in the open
where sunlight can cause over-heating.
(2)
Cooler:
33o-35oF (SLOW THAW):
Seedlings thawed in
conventional cooler, 33o-35oF, will thaw much more slowly (about 3
weeks for bareroot seedlings). Thawing should be done gradually by
raising ambient setting 1oF every four days until the AMBIENT cooler
temperature reaches 33o-35oF. As SEEDLING temperatures reach 33o35oF, reset COOLER AMBIENT temperature to 32.5oF and hold there
until shipment.
Thawing will be more uniform at lower temperatures.
b. Air circulation: Uniform, rapid thawing requires good air circulation
around containers. Placing boxes or bags on pallets and spreading out
boxes or bags will improve air circulation around them. If space is
limited and containers can not be spread out, rotation of grouped
containers where inside containers are moved to outside and vice versa
will facilitate uniform thawing.
c. Species: Some species, such as pine, thaw more rapidly than others.
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65.43 - Post-thaw Options.
Planting: Unless seedlings are returned or maintained at 33o-35oF, planting must
occur immediately after thawing.
Further Storage: If seedlings are not planted immediately after thawing, they
must be kept in cooler storage until they are planted. Temperature should be at the
conventional storage temp of 33o-35oF. Thawed seedlings may be successfully kept
in cooler storage for a period of 4 to 8 weeks (Emerson, 1986; Hee, 1987; Myers,
1990). The length of time will depend on the species and the rapidity with which
various lots begin to break dormancy in storage. Seedlings should be planted as
soon as possible after thawing so that the physiological advantage gained by early
lifting and freezer storage is not lost (Eklund, p. 19).
65.44 - Handling of Frozen Seedlings. Frozen tissue is much more brittle than nonfrozen tissue. Frozen stock should be handled carefully and minimally to prevent
tissue damage.
Handling damage can be minimized by packaging seedlings in bags which are then
placed in cardboard boxes. Use of pallets and racks in storage can be used if
pallets/racks are not moved until seedlings are thawed (that is, thawing is done in
the freezer by converting to cooler). However, cardboard boxes are not necessary for
a successful frozen seedling storage program.
65.45 - Transportation of Frozen Seedlings. Seedlings can either be thawed prior to
transporting to field or shipped frozen with thawing at field location. The potential
for damaging frozen stock will be minimized if seedlings are thawed at the Nursery
before they are shipped to the District or field. Nursery thawing conditions are
consistent and well-monitored. The recommended treatment is for Nursery
thawing of frozen Stock.
Seedlings may be transported frozen, stored frozen at the District site, and then
thawed at the District or field site. If seedlings are PLANNED to be shipped frozen,
they should be packaged in bags within boxes to minimize handling and damage.
65.46 - Freezer Storage References.
Ekland, R. 1988. Frozen storage tree seedling study on the Winthrop and
Twisp Ranger Districts, Okanogan National Forest- A comparison of survival
and growth of fall lifted and frozen seedlings with conventional spring lifted
seedlings. USDA Forest Service, Silviculture Certification Paper, Pacific
Northwest Region.
Emerson, T. 1986. Unpublished data James W. Toumey Nursery files.
Watersmeet, MI.
Hee, S.M. 1987. Freezer storage practices at Weyerhaeuser nurseries.
Tree Planters Notes 38(3):7-10.
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McDonald, S.E., R.J. Boyd and D.E. Sears. 1983. Lifting, storage,
planting practices influence growth of conifer seedlings in the Northern
Rockies, USDA, Forest Service, Intermountain Forest and Range Experiment
Station, Ogden, UT, Research Paper INT-300, 12 p.
Morby, F.E. and R.A. Ryker. 1979. Fall-lifted conifers successfully
spring planted in southwest Idaho. Tree Planters Notes 30(3):27-29.
Myers, J. 1979. Fall lifting and frozen stock storage at the Coeur
d'Alene Nursery. Poster presented at 1987 Region 6 Silviculture Business
Meeting, Portland, OR.
Myers, J. 1990. Unpublished data. Couer d'Alene Nursery files. Coeur
d'Alene, ID.
Mullin, R.E. 1980. Water dipping and frozen over-winter storage of red
and white pine. Tree Planters Notes 31(3):25-28.
Mullin, R.E. and J.D. Parker. 1976. Provisional guidelines for fall
lifting for frozen overwinter storage of nursery stock. The Forestry Chronicle
52(1):22-25.
Ritchie, G.A. 1987. Some effects of cold storage on seedling
physiology. Tree Planters Notes 38(2):11-15.
66 - SHIPPING SEEDLINGS FROM NURSERIES. The shipping packaging must
protect seedlings from desiccation by maintaining high relative humidity, and from
physical damage by shielding them from crushing pressure and hard blows.
Seedlings are quite vulnerable during shipping.
Shipping vehicles must contain seedling racks and be able to maintain appropriate
short term seedling storage environment. The standards are the same as those
which must be maintained in nursery storage. Humidity must be in the 90-95
percent range to ensure that the seedlings do not become desiccated. Temperature
must be in the 1o-2oC (34o-36oF) range to ensure a low level of physiological
activity and maintenance of dormancy.
67 - RESPONSIBILITIES OF DISTRICT ON RECEIPT OF TREE SEEDLINGS.
Regional standards for stock quality are published in section 63.3. Districts should
report stock quality received from Forest Service Nurseries or Contract Nurseries.
When stock quality problems occur with Contract Nurseries, the Contracting
Officers Representative (COR) should be notified. Call the Forest Service Nursery
immediately if substandard conditions are detected.
67.1 - Stock Condition. If the stock is of poor quality, for example, excessive
temperatures, moldy, insufficient root, or root lengths beyond specified allowances,
a report shall be made immediately to the Nursery with a copy to the Regional
Reforestation Specialist. Notification of poor quality stock is normally channeled
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through the Forest stock coordinator. However, if the stock coordinator is
unavailable, Districts should contact the Forest Silviculturist before contacting the
Nursery and Reforestation Specialist directly.
The following indications of poor stock quality (as detailed in the next section) must
be reported within 7 days after receipt of seedlings:
1. Product temperature violations.
2. All dormancy violations.
3. Excessive mold in boxes.
4. Dry trees or roots.
5. Damaged packages.
6. Dead roots.
7. Discolored tops.
If the trees are received frozen, items 4, 6, and 7 can be reported with the violations
listed below. Some tree quality criteria cannot be assessed until the trees are being
processed for planting. These criteria, explained in detail in the next section, can be
reported when discovered at the time of processing. Items that can be reported
when the trees are processed are:
1. Root lengths.
2. Height and caliper standards.
3. Tree counts.
4. Inadequate root mass in container plugs.
67.2 - Temperature of Delivered Stock. The temperature of the delivered stock is
the first concern of the District. The shipper must maintain an air temperature of
0o-4oC (32o-39oF) in the shipping compartment of bareroot stock. The product
temperature of bareroot stock (inside box) should not exceed 2oC (36oF) at any time
during shipment. Above this temperature the heat of respiration begins to increase
at an exponential rate, and it may be difficult to stop the process in snow caches or
ice houses.
If the temperature of the stock is between 2oC (36oF) and 4oC (39oF) the District
should contact the Nursery and should sample the seedlings to determine the
condition of shipment.
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Sample the loads using soil type or digital electronic probe thermometers. Sample
as many containers as feasible up to 2 percent with an absolute minimum of three
containers. Insert thermometers into center containers (fully surrounded) and
leave for 2-3 minutes or until temperature equilibrates with inside box
temperature. Be sure the thermometer has been calibrated for accuracy by
checking it against a good mercury thermometer or placing in a glass of ice water,
0oC (32oF). Be sure to include samples from the top of the load.
If you find trees with inside box temperatures of over 2oC (36oF) notify the
Nursery's COR immediately; then:
1. Determine accurately how many boxes of trees are involved. All boxes
exceeding minimum standards may be rejected. If a 10 percent of the load has been
sampled and it has been determined that more than 70 percent of the sample
exceeds 4oC (39oF), the whole load may be rejected.
The District is not responsible for any costs associated with trees in the rejected
boxes.
2. Warm trees may be saved by rapid temperature drawdown. Send the trees
back to the nursery. If cooled promptly, they will suffer no appreciable damage and
can be reshipped and planted. The District is responsible for only the original tree
costs. No additional charges are assessed.
If spoiled trees are received, return them to the Nursery by the truck they came on.
Coordinate this with Nursery COR. Warm trees should not be put in snow caches
or ice houses as they may cause problems to trees already in storage. For container
stock the storage compartment shall be held between 2o-24oC (36o-75oF).
Violations of these conditions, or any damage to stock, should be reported
immediately to the Nursery.
67.3 - Assessment of Violation Other Than Temperatures. Nursery stock, in
general, is in good condition when delivered to the Districts. However, there is
always a risk of receiving poor stock and, therefore, stock should be checked for
quality when received.
Before checking for stock quality carefully read the Regional guide for Planting
Stock Standards found in section 53.3.
67.4 - Bareroot Stock.
1. Root Length. Length of primary or tip roots should be 12 inches, or some
other requested root length.
2. Live roots. Check for live versus dead roots by simply stripping the outer
layers of cork and bark from the roots with a pocket knife or finger nail to expose
the steele. This tissue is white in healthy roots and brown to yellow tan in dead
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roots. The brownish color is due to oxidation similar to that of a cut apple which
has been left exposed.
Tree boxes can be checked by taking a tree from the top, center, and bottom of the
box. Do not be alarmed to find the roots have died back half an inch or so from the
cut ends. This is normal. Also, in some species (especially Douglas-fir) a portion of
the root system may die with no apparent adverse effect to the tree. However, if
more than 10 percent of the roots are dead more than 15 percent of their length on
more than 5 percent of the trees, this should be reported.
3. Root Activity. Check roots for the presence of white growing tips.
Usually, few will be present because soils are relatively cold at lifting time (late
winter or early spring) and tender growing tips may be left behind in the beds.
Storage temperatures are too low for root growth on all but a few species (larch,
lodgepole and true firs, for instance). However, roots do not experience dormancy as
top terminals do, so some activity may occur in storage. Root activity in storage is
not as frightening as top activity is. Tops should be less than 1/2 centimeter in
length and not numerous, although white buttons or elongations on root ends may
be very numerous without causing alarm.
4. Top Caliper and Height. Nursery grading standards for both top height
and caliper are listed in section 63.3. At least 95 percent of the stock packed should
meet these standards or the requested specifications on Lifting Request.
5. Color. The foliage of healthy stock is green. A purple cast is acceptable in
lodgepole pine. Western larch is deciduous and whatever needles are retained are
last year's and are dead or soon will be. In other species red or brown colors or
spotting is indicative of unhealthy stock. Needles may be shaded toward yellow
green without causing alarm. All discoloration except the purple tinge should be
reported if more than 15 percent of the trees appear red or brown or with red-brown
mottling.
6. Lammas Growth. Lammas growth (abnormal late season growth by
terminal or lateral buds) has normally been a problem only in lodgepole pine, and to
a lesser extent, in ponderosa pine. This late season growth may cause two problems
with nursery stock. The late formed growth may be succulent and not hardened off
properly. Perhaps even worse, trees in this condition may not store well at
temperatures above 1o-2oC (34o-36oF). Field experience has shown that lodgepole
pine with lammas growth will break dormancy and/or spoil under storage conditions
suitable for other species.
Three types of lammas growth are of primary concern here.
a. Lammas shoots. Shoots which develop by bursting and elongation of
the current year terminal bud. This will result in 2-0 stock having the
appearance of 3-0 with the last growth whorl in varying degrees of
hardening off.
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b.
In long buds the current year terminal elongates with no
corresponding bud burst. Elongation may be from a few millimeters to 4
or 5 inches. The result may be a long, slender, succulent terminal with
a soft unhardened terminal.
c. Proleptic shoots.
buds.
Shoots that emerge from current year's lateral
While the classes are clearly defined, lammas will vary in gradation and some trees
will exhibit growth that is a mixture of the classes.
Lots with green succulent growth and soft buds in more than 5 percent of the trees
should be reported on the tree quality assessment form.
7. Dormancy. Dormancy release is revealed usually by candle extension and
softening in pines, and by bud enlargement and softening in most other commonly
planted species. Dormant buds usually appear dark while active buds will be
lighter because bud scale edges hidden in firm dormant buds will become exposed
when swelling begins. Species which candle give unmistakable evidence of
dormancy release. As candles begin to grow on seedlings stored in a horizontal
position, new growth will turn upward at a 90o angle in response to geotropism. If
new green needles appear, dormancy is unquestionably broken.
However, if buds are visibly active, physiological awakening has progressed to the
point where storage life of seedlings is drastically reduced. Dormancy release is an
indication of serious tree quality problems and should be reported immediately. It
means either that trees were lifted after the lifting window closed or that storage or
shipping temperature became too high for too long a period. If trees cannot be
planted immediately when terminal activity becomes apparent, they probably
should be discarded.
8. Packing Material. The packing material and roots should feel cool, moist,
and pliable to the touch. Roots that feel stiff and dry may be damaged. If dry roots
are suspected, cambium condition should be checked. Plant moisture stress should
also be checked if a pressure bomb is available. A PMS of 5 bars (atmospheres) or
less is preferable and trees with stresses over 10 bars should be reported
immediately. Trees with stresses up to 10 bars should recover within hours after
dipping and burlap wrapping to stresses of below 5 bars. Trees stresses over 15
bars have a high risk of suffering permanent physiological damage. Trees that feel
dry and show any evidence of damage due to drying should be reported as not
meeting standards.
9. Mold or Fungus Mycelium. The presence of visible mycelium (white or
black threads on strands of fungal tissue) may be cause for some concern. However,
most molds are either saprophytic (living on dead substances) or mycorrhizal on the
roots. Mats of mycelium on the foliage are of major concern. Fungi associated with
strong odors, brown cambial tissues in roots or stem, or spotting of needles are of
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major concern. Fine strands or tufts in the roots without the other symptoms are
not usually harmful.
10. Mud or Dirt in Boxes. Trees packed in boxes should be relatively clean.
Excess mud and dirt will promote fungal problems and foliage discoloration.
11. Free Moisture. Mold growth will be favored by free moisture in the
storage containers. Presence of free moisture on the seedlings or in the bottoms of
containers should be reported on the seedling quality assessment form.
12. Damaged Packages. Packages should not be torn or broken to the point
where seedlings are exposed to outside air.
67.5 - Container Stock.
1. Adequate Root Mass. The root mass should be developed to the point the
plug can be extracted from the container and still retain its original form.
Excessive root development and resultant pot binding may be damaging to
containerized seedlings. To check this, shake the plug until the media pulls away
from the roots. Most of the roots should be pointed downward with the lateral
horizontal roots smaller and not circling the plug. If the horizontal roots are thick
and flattened and the plug stays in a thick net the shape of the original plug, the
tree is suffering from pot binding.
2. Root Media Moist. Roots and plug should be moist when seedlings arrive.
Moisture stress should be below 10 bars.
3. Live Roots. Roots can be checked for live tissue using the same technique
as described previously for bareroot stock.
5. Caliper and Height. The bareroot direction for caliper and height are
appropriate for container stock as well.
5. Sturdy, Standing Erect. Individual trees must be capable of standing
erect individually.
6. Dormancy. For fall delivery, terminal buds should be evident.
growth is permissible.
Root
For spring delivery, ideally, stock should be dormant with tight buds and little or no
new root growth. The main disadvantage with nondormant container stock is that
the new top growth is easily broken off. However, since root systems are essentially
intact, will be minimally disturbed, and do not have to be regenerated, the container
seedling survival is not affected as is bareroot stock.
7. Color. The color standards described for bareroot stock are applicable to
container also.
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8. Mold Absent. Any signs of strands or threads of mycelium on the tree
foliage or buds should be noted. Gray mold (Botrytis sp.) is of major concern. Check
carefully for myceliums on the foliage.
68 - LOCAL STORAGE AND SHIPMENT TO THE FIELD. The local storage and
shipment of seedlings to the field are critical in assuring reforestation success.
68.1 - Storage. Temperature should be held between 1o and 2oC (34o and 36oF) and
relative humidity greater than 90 percent within seedling packages so that
seedlings do not break dormancy or become desiccated. The critical area for
seedling environment is within the storage packages, not in the ambient spaces of
the tree coolers. Coolers with ambient temperatures of -1o-0oC (30o-32oF) can be
expected to maintain seedling packages at 1o-2oC (34o-36oF). Even though cooler
space may be -1oC (30oF), within packages temperatures as high as 4oC (39oF)
have been measured when inadequate racking systems or closely stacked boxes
have prevented air circulation. Root-mass temperatures 8oC (46oF) above ambient
temperature have been reported under conditions of poor air circulation.
Stored seedlings should be monitored to assure the PMS is maintained below 5
bars. Stresses higher than 5 bars indicate a problem requiring immediate
correction. Humidities of 90 percent in packages should be adequate to maintain
storage PMS below 5 bars.
68.11 - Tree Storage Standards. When storing bareroot stock on the District, the
following standards must be met:
1. The product temperature (inside package temperature) must be kept below
2oC (36oF) at all times. This will require facilities that allow for ambient
temperature settings of -2o-1oC (28o-34oF). Ideal product temperature is 0-1oC
(32o-34oF) and it is better to drop to -2oC (28oF) than to go above 2oC (36oF).
2. Relative humidity in the storage compartment must be kept at 90 percent.
Humidity less than this can dry seedlings out when stored over a period of several
weeks.
3. Tree packages must be racked and spaced to allow for air flow between the
packages.
68.2 - Shipment to Planting Site. Keep seedlings cool and moist at all times.
Delicate root surfaces may be damaged in seconds by exposure to wind and low
humidities. Warm temperatures will cause seedlings to use up their food reserves
rapidly and induce dormancy release. Never allow seedling packages to be shipped
in direct sunlight. Inside package temperature must never rise over 4oC (39oF).
68.21 - Acclimatization. This is the process of slowly bringing seedlings from a
dormant state to an active state. This process is thought to allow time for seedlings
to adjust to the more harsh field conditions without being stressed.
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Seedlings that are planted while in a dormant state are immediately exposed to a
hostile environment. Needles warm up from solar heating or dry out from wind
movement. They begin to transpire moisture before roots are ready to replace it.
Shoot desiccation may occur.
While in storage, seedlings have been slowly depleting food reserves in the tops and
roots. This food reserve is further reduced after planting, unless seedling shoots are
fully photosynthetically active.
There is general disagreement among scientists on the mechanisms or the need for
acclimatization of seedlings. It has not been shown to be be beneficial. However,
neither has it been shown to be detrimental. Current acclimatization methods are
associated with Jelly Rolling (section 69.21). Seedlings are left up to 24 hours in
shelters (usually tents) at planting sites to permit them to gradually come up to the
ambient temperature of the site. This process is not recommended nor is it
discouraged. If it is used, duration should not be longer than 24 hours, and
seedlings must not be allowed to freeze as they are coming out of dormancy, and the
probability of damage would be high.
ACCLIMATIZATION OF STOCK IS NOT REQUIRED BUT IS OFFERED ONLY
AS A METHOD OF REDUCING PLANTING SHOCK TO SEEDLINGS.
68.22 - Transport of Seedlings. Seedlings must be protected constantly from
extremes of temperature and moisture stress. Closed canopied vehicles are the
preferred method of transporting seedlings to the field if kept at 4 oC (39oF). If
open-bed vehicles are used, seedlings SHALL BE covered with space blankets or
reflective mylar tarps. Canvas tarps are WORSE than nothing. The cover should
allow some air circulation to prevent heat buildup or self-heating by seedlings.
CAUTION: The beds of vehicles heat up thus the seedlings should be insulated
from the bed to prevent heating.
68.3 - Storage of Seedlings at Planting Site. At the planting site, seedlings should
be kept in a cool, shaded, and well-ventilated location until they are used. Trees,
logs, and canvas shelters other than tarps can be used to provide shade. Seedlings
should be protected from freezing when left out in cold weather. Bags or boxes of
seedlings should not be stacked more than two or three high to prevent both
crushing and heat buildup in the center of the piles. To avoid damaging the
seedlings, planters must not be allowed to throw, handle carelessly, sit, or walk on
bags or boxes of seedlings.
Normally, seedlings that arrive first should be planted first. However, seedlings in
torn packages should be given priority if excessive dryness is indicated.
Tears in packages should be repaired when they occur!
68.4 - Root Pruning in the Field. As a general principle, root pruning on the
planting site is an emergency measure, to be avoided if at all possible.
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ROOTS MUST NOT BE TORN OR PULLED OFF!
Root pruning by the Districts should be minimized as much as possible. Pruning
just prior to planting is detrimental because root ends do not have time to callus
over and generate new growing centers prior to planting. Some Districts avoid
pruning completely. Long laterals are just stuffed in the planting hole. As long as
only one or two laterals are involved and are not wrapped around the root systems,
this may be a better practice than pruning. If this option is chosen, it may require a
planting contract amendment.
If selective pruning is chosen, it should be kept at an absolute minimum. Do not cut
off one-half to an inch of roots. Only seedlings with excessively long roots should be
pruned.
Pruning must be done at the time of wrapping or placement in planting bag,
NEVER BY THE PLANTER. Scissors or paper cutters are recommended for root
trimming while the seedlings are laid flat.
68.5 - Care of Seedlings by the Planters. Planters handling seedlings must take the
following precautions:
1. Tree seedlings must be protected at all times from drying, heating,
smothering, freezing, crushing, drowning, abrasion, rapid temperature fluctuations,
or contact with injurious substances.
2. Seedlings stored in shipping containers must not be exposed to direct
sunlight. Punctured or torn containers must be promptly resealed. Containers of
seedlings shall be separated to provide free air movement.
3. Seedlings shall not be removed from shipping containers until needed for
preparation for planting.
4. Tree seedlings are to be planted or prepared as received without further
root or top pruning or culling. If pruning or culling appears necessary, or if mold,
dry roots, evidence of injury or dying is seen, the condition shall immediately be
reported to the individual in charge of the planting project.
5. Seedlings that are frozen shall not be handled until completely thawed.
6. Seedlings in planting bags shall have only their tops exposed. Burlap
wrapped seedlings shall have the wrapping loosened, just prior to planting, to allow
easy extraction of seedlings from the roll.
7. NO SEEDLING SHALL BE REMOVED FROM PLANTING BAGS UNTIL
IMMEDIATELY BEFORE PLANTING IN A PREPARED HOLE.
8. Seedlings shall be gently removed, one at a time, to prevent stripping or
other injury, and quickly and gently inserted into the planting hole.
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9. Seedlings carried in planting bags or trays shall not exceed the amount that
can be carried and removed without injury, or which can be planted before critical
heating or drying occur. Trees placed in bags will be planted and not returned to
storage.
10. Separate seedlings to be planted by shaking the roots loose in the shipping
container, taking care not to strip them.
11. Use planting bags that are not holed or torn.
69 - SPECIAL CONSIDERATIONS FOR CARING FOR PLANTING STOCK.
69.1 - Suspension of Planting. Planting under certain weather conditions may be a
waste of time, funds, and seedlings. These conditions will vary depending on the
species being planted and the subregional area where the planting is being done.
Factors to consider are soil moisture and temperature, air temperature, relative
humidity, and wind speed. Several references exist to help make decisions on when
to and conversely when not to plant seedlings. Local administrative units must
supplement this handbook material with details applicable to local conditions.
69.11 - Soil Moisture. Soil moisture will usually be adequate during the planting
season if site preparation has been adequate. If no or limited vegetation is present
moisture will not be pumped out. Several computer programs have been written
using local climatic history and soil moisture retention curves which can be adapted
for localized conditions. See Appendix A for references.
69.12 - Atmospheric Moisture Demand. High moisture demand in the atmosphere
can be very damaging to exposed seedling roots. Three things which contribute to
high demand, a humidity index, wind speed, and temperature have been
incorporated into a pair of tables to identify combinations which may be particularly
damaging. These tables should be used to alert oneself to marginal conditions when
a damaging combination occurs, and remedial measures to protect roots should be
used. For instance, insulated planting bags should be used. Also, root systems
should be dipped in water or a vermiculite or peat moss slurry. If conditions are
deep in the hazard zone of the table, it may be wise to delay planting until late in
the day and plant until dark when trees are then entering a recovery period.
69.13 - Frost and Snow. Planting should be suspended if the ground cannot be
scalped free of frost crystals or snow. Planters must be instructed not to use snow
or frozen soil to back fill planted trees. The adverse consequences of planting in
frozen ground can be reduced by planting south facing slopes first until the ground
has warmed up on other aspects.
69.2 - Special Packaging of Seedlings.
69.21 - Jelly Rolling. Seedlings are rolled into a water-saturated burlap sheet, with
tops exposed and roots enclosed. A moisture-holding medium, such as sphagnum,
peat moss, or horticultural grade vermiculite is packed around roots for additional
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protection. This "jelly roll" of seedlings is slipped into the planter's bag, and the
seedlings are extracted one at a time for planting.
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The burlap used in "jelly rolling" must be at least 18" X 30" in size to accommodate
seedlings properly. If new burlap is used it should be soaked for a minimum of 24
hours before using. If new burlap is used without soaking this period it will wick
moisture from the roots.
69.22 - Root Dipping. Dipping roots in aqueous solutions of various moistureretaining products or in plain water immediately before seedlings are bagged for
planting helps protect roots from desiccation during the short time they are exposed
before planting. Horticultural grade vermiculite or peat moss are the two most
frequently used materials. Insulation grade vermiculite MUST BE avoided because
it is waterproof.
69.23 - Insulated Planting Bags. Planting bags insulated with polyurethane foam
or similar materials can be used to protect seedling roots when climatic conditions
become warm and dry. Waterproof bags with foam linings are particularly effective
in keeping seedlings moist and cool during the hours required to plant the number
of seedlings they contain.
APPENDIX A - REFERENCE LIST.
Baumgartner, D. M. and R. J. Boyd, eds. 1976. Tree Planting in the
Inland Northwest. Washington State Univer.,Coop. Ext. Serv., Pullman,
Wash. 311p.
Cleary, B.D., R.D. Greaves, and R.K. Hermann, eds. 1978. Regenerating
Oregon's Forests. Oregon State Univ. Ext. Serv., Corvallis. 287p.
Cleary, B.D., and D.R. DeYoe. 1982. Seedling Care and Handling. Oregon
State Univ. Ext. Serv., Corvallis. Ext. Circular 1095. 4p.
Dobbs, R.C., D.G. Edwards, J. Konishi, and D. Wallinger. 1976.
Guidelines to Collecting Cones of British Columbia Conifers. British Columbia
For. Serv./Canadian For. Serv., Victoria, B.C., Joint Rep. No. 3. 98p.
Duryea, M.L. and T.D. Landis, eds. 1984. Forest Nursery Manual
Production of Bareroot Seedlings. Oregon State Univ. Forestry Res. Lab.,
Corvallis. 386p.
Duryea, M.L., ed. 1985. Evaluating Seedling Quality: Principles,
Procedures, and Predictive Abilities of Major Tests. Oregon State Univ.,
Forest Res. Lab., Corvallis. 143 p.
Hedlin, A.F., H.O. Yates III, D.C. Tovar, B.H. Ebel, T.W. Koeber, and
E.P. Merkel. 1980. Cone and Seed Insects of North American Conifers,
Canadian For. Serv., U.S.D.A. For. Serv. and Secretaria de Agricultura y
Recursos Hidraulicos, Mexico.
Hermann, R.K., D.P. Lavender, and J.B. Zaerr. 1977. Lifting and Storing
R-6 AMENDMENT 2409.26b-92-2
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Western Conifer Seedlings. Oregon State Univer., Forest Res. Lab., Corvallis.
Res. Paper 17. 8p.
Hocking, D.A. and R.D. Nyland. 1971. Cold storage of coniferous
seedlings, a review. Applied Forestry Res. Institute, State Univ., New York,
Coll Forestry, Syracuse. Res. Rep. 6. 70p.
Hopkins, J.C. 1975. A review of moulding of forest nursery seedlings in
cold storage. Can. Forestry Serv., Pacific Forest Res. Centre, Victoria, B.C.
Rep. BC-X-128. 16p.
Lopushinsky, W. and T. Beebe. 1976. Relationship of Shoot-Root Ratio to
survival and growth of outplanted Douglas-fir and Ponderosa pine seedlings.
U.S.D.A. Forest Serv., Pacific NW Forest and Range Exp. Sta., Portland,
Oregon. Res. Note PNW-274. 7p.
Lopushinsky, W. 1986. Jelly Rolling.
McDonald, S.E., R.J. Boyd, and D.E. Sears. 1983. Lifting, storage,
planting practices influence growth of conifer seedlings in Northern Rockies.
U.S.D.A. Forest Serv., Intermountain Forest and Range Exp. Sta., Ogden,
Utah. Res. Paper INT-300. 12p.
Navratil, S. 1973. Pathological and physiological deterioration of
planting stock in cold storage (Silviculture review). Timber Seminar. Thunder
Bay District, Thunder Bay, Ontario. Unpubl. rep. 27p.