2409.26f,300
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FSH 2409.26f - SEED HANDBOOK
R2 AMENDMENT 2409.26f-93-1
EFFECTIVE 6/15/93
CHAPTER 300 - SEED PRODUCTION
Contents
310
CONE AND SEED DEVELOPMENT
320
FREQUENCY OF SEED CROPS
R2 AMENDMENT 2409.26f-93-1
EFFECTIVE 6/15/93
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Basic to any seed collection program is a good working knowledge of the biology of seed production including seed
development period; minimum seed bearing age; seed production per tree, stand, and geographic variation; timing of
flowering seed maturity and dispersal; and cone crop frequency.
310 - CONE AND SEED DEVELOPMENT. The seed development period or length of time required for development
of seed from floral initiation to seed maturity, is an important criterion to use in timing and planning of seed
collection. For all coniferous species in the Rocky Mountains, reproductive structures are initiated the summer prior
to their emergence in the spring. After the reproductive structures have emerged from their buds in the spring, the
length of time until mature seed is produced differs between the pines and other species. For example, in the pines
it takes about 18 months from the time of pollination to seed fall, while in the spruces, Douglas-fir and true firs, only
about 6 months elapses between pollination and seed fall. (Exhibit 1). In general, the reproductive structures of
Douglas-fir emerge first, followed by ponderosa pine, lodgepole pine, then the spruces and true firs. Fertilization in
the spruces, Douglas-fir and the true fir usually takes place 2-4 weeks after pollination, while in the pine,
fertilization occurs about 12 to 13 months after pollination. Immediately after fertilization, rapid development and
enlargement of cones and seed follows. Seed in the central Rockies usually matures in late August through
September and early October. Seed fall then begins usually within 2 to 4 weeks of seed maturity or about late
August into October. With some species seed fall may occur throughout the following winter. Seed in serotinous
(closed) cones of lodgepole, however, may be retained for several years without losing viability.
Age when seed production begins is genetically controlled and locally affected by growth rate (soils, climate, and
competition), latitude (day length) and elevation. Lodgepole pine may begin to produce seed as early as age 3-5
years, and considerable cone production may occur on individuals at age 10. Ponderosa pine begins to produce seed
at slightly older ages (6-20 years), then Engelmann spruce (16-25 years), Douglas-fir (20 years), and white fir (40
years).
Viable seed can be produced on most forest trees at any age when reproduction structures are present and adequate
and effective pollination and fertilization takes place.
Times at which flowering occurs are probably not very important from the field manager's viewpoint. However,
observations of flowering and development of cones can be used to estimate potential cone and seed crops. These
observations will aid in the planning process for needed seed collection.
Timing of cone and seed maturity and seed fall is critical for the collection of seed; that is, seed should be collected
when it is mature but before normal seed fall occurs. Because timing will vary with species, year, and location,
periodic field checks are needed to determine cone and seed maturity.
R2 AMENDMENT 2409.26f-93-1
EFFECTIVE 6/15/93
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310 - Exhibit 01
CONE AND SEED DEVELOPMENT
SEE THE PAPER COPY OF THE MASTER SET
FOR SECTION 310 EXHIBIT 01.
R2 AMENDMENT 2409.26f-93-1
EFFECTIVE 6/15/93
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310 - Exhibit 02
SEED PRODUCTION FACTS OF MAJOR TREE SPECIES OF CENTRAL ROCKY MOUNTAINS
TREE
SPECIES
SEED
MINIMUM
LARGE SEED
DEVELOPMENT SEED-BEARING
CROP
FLOWERING
PERIOD
AGE
FREQUENCY
DATES
CONERIPENING
DATES
SEED
DISPERSAL
DATES
CONE
RIPENESS
PRE-RIPE COLOR RIPE
Pinus
ponderosa
var.
scopulorum
3 yrs.
6-20
3, 2-5 yrs.
May-June
Aug.-Sept.
Sept.-Jan.
Green
Purplish
Brown
Pinus
contorta var.
latifolia
3 yrs.
5-10 yrs.
2, 1-4 yrs.
June-July
Aug.-Sept.
Sept.-Oct.
Purple
Green
Light Brown
2 yrs.
16-25 yrs.
3, 2-6 yrs.
June-July
Aug.-Sept.
Sept.-Oct.
Green
tinged with
crimson
Shining
Brown
2 yrs.
20 yrs.
5, 3-11 yrs. April-May
Aug.-Sept.
Aug.-Sept.
Green
BrownPurple
Green
Olive
GreenPurple
Picea
engelmannii
Pseudotsuga
menziesii
var. glauca
Abies
concolor
2 yrs.
40 yrs.
3, 2-4 yrs.
May-June
Aug.-Sept.
Sept.-Oct.
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320 - FREQUENCY OF SEED CROPS. Most coniferous tree species do not produce good seed crops annually.
Moderate to good seed crops may be produced every 2 to 5 years, or sometimes as infrequently as every 10-15 years,
depending upon species, environmental variables, geographic location, and pest incidence (Exhibit 2, section 310).
Lodgepole pine seed crops are the most frequent with moderate crops produced almost every year and large crops
produced about every other year. Because of high costs of seed collection when cone crops are poor, seed should be
collected only in years when moderate to heavy seed crops are available. Good crops during the 17 year period 19641980 in Engelmann spruce, ponderosa pine, and Douglas-fir occurred in the following years:
Engelmann spruce
1964
1967
1971
1974
1977
1980
Ponderosa pine
1965
1971
1974
1977
1979
1983
Douglas-fir
1964
1974
1977
1980
Seed yield, per bushel of cones, is much higher during good seed crop years than during poor seed years. For
example, in Engelmann spruce the yield of seed (lb) per bushel of cones in the good seed years 1977 and 1980 was
0.71 and 0.64, respectively. In 1978 and 1979 when cone crops were light, yield of seed per bushel of cones was only
0.45 and 0.42. Also, during good seed years, a lower percent of seed is lost as a result of insect and disease
incidence.