United States
Department of
Agriculture
Forest Service
Pacific Southwest
Research Station
General Technical
Report PSW-GTR-143
IMPROVING PLANTING
STOCK QUALITY—THE
HUMBOLDT EXPERIENCE
James L. Jenkinson
James A. Nelson
May E. Huddleston
Jenkinson, James L.; Nelson, James A.; Huddleston, May E. 1993. Improving planting stock
quality—the Humboldt experience. Gen. Tech. Rep. PSW-GTR-143. Albany, CA: Pacific
Southwest Research Station, Forest Service, U.S. Department of Agriculture; 219 p.
Abstract: A seedling testing program was developed to improve the survival and growth potential of
planting stock produced in the USDA Forest Service Humboldt Nursery, situated on the Pacific Coast
in northern California. Coastal and inland seed sources of Douglas-fir and eight other conifers in the
Pacific Slope forests of western Oregon and northern California were assessed in both nursery and
field studies. Seedling top and root growth capacities were evaluated just after lifting and after cold
storage, and stored seedlings were tested for survival and growth on cleared planting sites in the seed
zones of origin. Safe lifting and cold storage schedules were defined, and seedling cultural regimes
were formulated to produce successful 1-0, 1-1, and 2-0 stock types. Testing demonstrated the
critical elements of reforestation and proved that rapid establishment is attainable on diverse sites.
Accomplishments of the Humboldt program recommend similar programs for other forest nurseries
and their service regions.
Retrieval terms: artificial regeneration, nursery management, plantation establishment, reforestation,
seedling culture, seedling root growth capacity, seedling survival; Abies concolor, A. grandis, A.
magnifica var. shastensis, A. procera, Libocedrus decurrens, Picea sitchensis, Pseudotsuga menziesii
var. menziesii, Thuja plicata, Tsuga heterophylla
The Authors
James L. Jenkinson is research plant physiologist, Institute of Forest Genetics, Pacific Southwest
Research Station, Albany and Placerville, CA. James A. Nelson is supervisory forestry technician and
seedling cultural specialist, Humboldt Nursery, Six Rivers National Forest, Pacific Southwest Region,
McKinleyville, CA. May E. Huddleston is an editor-writer and publications consultant in Petaluma,
CA, and former technical publications editor, Pacific Southwest Research Station, Albany, CA, and
Intermountain Research Station, Ogden, UT.
Acknowledgments
Michel J. “Mitch” Knight, Pacific Southwest Region reforestation specialist (retired), conceived and
aggressively backed Humboldt Nursery’s seedling testing program. Edith Albro, Barbara Christie
(retired), Alta Colson (retired), Lavelle Frisbee, Dorothy Phillips (deceased), and Sally Thompson in
1975-90 sampled 105 seed sources, evaluated growth capacities of 20,000 seedlings, processed
80,000 for field performance tests, and managed a dozen studies of nursery culture alternatives. Lee
Whitman, industrial equipment mechanic, and Brian Konnersman, building maintenance worker,
helped design and build the test equipment and greenhouse, office-head house, and cold storage
facilities. Some 400 cooperators — USDA Forest Service and USDI Bureau of Land Management,
Pacific Southwest and Northwest Regions — planted and measured seedlings in 100 tests on cleared
sites in the Pacific Slope forests of California and Oregon. Diana Doyal, computer programmer
analyst, Institute of Forest Genetics, Pacific Southwest Research Station, Albany, CA, provided the
statistical analyses and graphics. Manuscripts were reviewed by John Fiske, reforestation forester,
Pacific Southwest Region, San Francisco; Mel Greenup, formerly forest silviculturist, Siskiyou National
Forest, OR, and now manager, Interregional Port-Orford-Cedar Program, Grants Pass, OR; Cynthia
Henchell, superintendent formerly at Humboldt Nursery, Six Rivers National Forest, CA, and now at
Wind River Nursery, Gifford Pinchot National Forest, WA; and William H. Scheuner, superintendent
(retired), Placerville Nursery, Eldorado National Forest, CA. Lindsay W. Olsen, photographer, Eureka
and Santa Rosa, CA, photographed operations at Humboldt Nursery and regeneration units on the
Gasquet Ranger District. Marlette Grant, civil engineering technician, Six Rivers National Forest,
provided computer support for table layouts. Bradford J. Kirby, computer consultant, Mountain View,
CA, drew the maps, refined graphics, and provided the finished layout.
Cover: Shown in Humboldt Nursery are (top pair) 2-0 and 1-1 Douglas-fir, (middle pair) 2-0 western
hemlock and western redcedar, (bottom pair) 2-0 Sitka spruce, and 1-0 red alder and Jeffrey pine.
IMPROVING PLANTING STOCK
QUALITY—THE HUMBOLDT
EXPERIENCE
James L. Jenkinson
James A. Nelson
May E. Huddleston
Publisher
Pacific Southwest Research Station
800 Buchanan Street
Albany, California 94710
Mailing address: P.O. Box 245
Berkeley, CA 94701-0245
Telephone: 510-559-6300
May 1993
USDA Forest Service Gen. Tech. Rep. PSW-GTR-143. 1993
Douglas-fir of 70-inch dbh on Fox
Ridge, Gasquet Ranger District, Six
Rivers National Forest
CONTENTS
REFORESTATION AND THE NURSERY .................................... 1
THE REFORESTATION PROCESS .............................................................1
NURSERY PRACTICE AND STOCK QUALITY ..........................................3
SEEDLING TESTING AT HUMBOLDT NURSERY .....................................3
Physiographic Regions Served ..............................................................6
Planting Stock Produced .......................................................................7
The Nursery Environment ......................................................................8
Standard Cultural Practices ...................................................................9
The Testing Program ...........................................................................11
FOCUS OF THIS REPORT .........................................................................18
FIGURES AND TABLES .............................................................................18
ASSESSING PLANTING STOCK QUALITY .............................. 23
THE PROGRAM DESIGN ...........................................................................23
PROGRAM ACCOMPLISHMENTS ............................................................24
STANDARD TESTING PROCEDURES .....................................................27
Seed Source Selection ........................................................................27
Monitoring Nursery Climate .................................................................27
Seedling Sampling and Handling .........................................................28
Growth Capacity Tests .........................................................................29
Field Performance Tests ......................................................................31
Variance Analyses ...............................................................................32
Correlation Analyses ............................................................................33
SEED SOURCE ASSESSMENTS—DOUGLAS-FIR .................. 35
SEED SOURCES ASSESSED ...................................................................35
SEASONAL PATTERNS OF GROWTH CAPACITY .................................37
Autumn-Winter Climate ........................................................................40
TGC in Autumn-Winter .........................................................................40
RGC in Autumn-Winter ........................................................................41
Practical Implications ...........................................................................46
COLD STORAGE CHANGES OF TGC AND RGC ....................................47
TGC at Planting Time ..........................................................................52
RGC at Planting Time ..........................................................................52
Practical Implications ...........................................................................53
SEED SOURCE LIFTING WINDOWS ........................................................53
Field Survivals ......................................................................................53
Lifting Windows and Tree Growth ........................................................59
NURSERY MANAGEMENT GUIDES .........................................................69
Safe Cold Storage ................................................................................71
Lifting Window Types ...........................................................................71
Scheduling Untested Sources .............................................................72
PLANTATION ESTABLISHMENT ..............................................................72
RGC, Site, and Survival .......................................................................72
Animal Damage ...................................................................................78
Tree Growth .........................................................................................78
ii
USDA Forest Service Gen. Tech. Rep. PSW-GTR-143. 1993
SEED SOURCE ASSESSMENTS—OTHER CONIFERS ...........85
SEED SOURCES ASSESSED ...................................................................87
SEASONAL PATTERNS OF GROWTH CAPACITY .................................87
TGC in Autumn-Winter ........................................................................87
RGC in Autumn-Winter ........................................................................91
COLD STORAGE CHANGES OF TGC AND RGC ....................................94
TGC at Planting Time ..........................................................................95
RGC at Planting Time ..........................................................................95
Practical Implications ...........................................................................97
SEED SOURCE LIFTING WINDOWS ........................................................99
RGC, Site, and Survival .....................................................................102
Lifting Windows and Tree Growth .....................................................103
NURSERY MANAGEMENT GUIDES .......................................................112
ASSESSING NURSERY CULTURE ALTERNATIVES .............115
GROWING SEEDLINGS FOR 1í0 PLANTING STOCK ..........................115
Soil Preparation for Early Sowing ................................................................. 118
Seed Treatment and Germination ................................................................ 119
Seed Chilling and Seedling Emergence ....................................................... 119
EVALUATING SIZE AND PERFORMANCE OF 1í0 STOCK .................121
TOPDRESSING EARLY SOWINGS WITH NPS ......................................127
USING 1í0 STOCK IN PLANTING PROGRAMS ....................................131
DETERMINING NURSERY SOWING WINDOWS ...................................132
Winter and Spring Sowings .......................................................................... 133
Seedling Growth, Stocking, and Grade ........................................................ 135
Sowing Windows and 1-0 Stock Yield .......................................................... 137
Sowing Windows and Field Survival and Growth ......................................... 140
Management Implications ............................................................................. 144
CARRYING 1í0 FOR 2í0 PLANTING STOCK .......................................145
UNDERCUTTING EARLY SOWINGS FOR 2í0 STOCK .........................148
Single and Double Undercuts Compared ..................................................... 148
Management Implications ............................................................................. 155
TESTING PROPOSED PRACTICES ........................................................161
Mycorrhizal Inoculation ................................................................................. 161
Root Wrenching ............................................................................................ 163
Freeze Storage ............................................................................................. 166
Precooler Storage ......................................................................................... 168
EVALUATING FALL AND WINTER PLANTING .....................................170
MOVING INTO THEƍ90ƍS ..........................................................175
REFERENCES ..........................................................................181
APPENDIX ................................................................................187
A. HUMBOLDT ORIGINS .........................................................................187
B. REFERENCE TABLES ........................................................................188
C. GROWTH CAPACITY TEST INSTRUCTIONS ....................................210
D. PLANTING SITE DESCRIPTIONS ......................................................212
E. FIELD TEST DATA FORMS ................................................................218
USDA Forest Service Gen. Tech. Rep. PSW-GTR-143. 1993
iii
Douglas-fir timberlands, Gasquet Ranger District: View of Fox Ridge from
Muzzleloader Ridge, and below, view of recently logged Gordon Creek unit
2/4 from Jones Ridge unit 2, planted 18 years earlier
USDA Forest Service Gen. Tech. Rep. PSW-GTR-143. 1993