PACIFIC SOUTHWEST Forest and Range FOREST SERVICE U. S. DEPARTMENT OF AGRICULTURE P.O. BOX 245, BERKELEY, CALIFORNIA 94701 Experiment Station USDA FOREST SERVICE RESEARCH PAPER PSW-99 /1974 CONTENTS Page Summary ................................................... 1 Introduction ................................................. 3 Methods .................................................... 3 Testing Fresh Seeds ....................................... 3 Testing Stratified Seeds .................................... 3 Seedling Vigor Tests ...................................... 4 Artificial Ripening Trial ................................... 4 Other Observations ........................................ 4 Results and Discussion ....................................... 5 Cone Specific Gravity ..................................... 5 Seed Germination, byCollection Date ....................... 5 Seed GerminationandCone Specific Gravity ................ 7 Red Fir Seedling Vigor .................................... 9 ArtificialRipening of White Fir Seeds ....................... 9 OtherMaturity Indices ..................................... 9 Application ................................................. 10 Literature Cited.............................................. 12 THE AUTHOR WILLIAM W. OLIVER is doing silvicultural research on Sierra Nevada conifer types with headquarters at Redding, California. He earned a B.S. degree (1956) in forestry from the University of New Hampshire, and an M.F. degree (1960) from the University of Michigan. A native of Pennsylvania, he joined the Station in 1962, after working for the Michigan Department of Natural Resources. ACKNOWLEDGMENT I thank the California Division of Forestry for the use of the Latour State Forest in the study reported in this publication. SUMMARY Oliver, William W. 1974. Seed maturity in white fir and red fir. Pacific Southwest Forest and Range Exp. Stn., Berkeley, Calif. 12 p., illus. (USDA Forest Serv. Res. Paper PSW-99) Oxford: 232.218:232.312.1 [ + 174.7 Abies concolor + 174.7 Abies magnifica]. Retrieval Terms: Abies concolor; Abies magnifica; germination tests; cone collection; Latour State Forest; California. Low viability of white fir and red fir seeds often is cool, moist environment for 4 weeks yielded seed the result of collecting immature seeds. Seed handlers which germinated as completely and speedily as need to know when acceptable seed viability is stratified seeds from mature cones. This result sup­ reached in the maturing cone. For this they need ports the observation by others that maturation of easily measured cone and seed characteristics that in­ seeds of many true firs can be completed inde­ dicate this point has been reached. In this study, sev­ pendently of the tree. Storing immature white fir eral cone and seed characteristics were evaluated as cones 2 weeks beyond beginning of seed fall boosted maturity indices for white and red fir. A limited test both speed and completeness of germination beyond of artificially ripening white fir cones was also made. that of stratified seeds from mature cones. This sug­ Cones from six white fir and eight red fir trees on gests that white fir requires some after-ripening for the west slope of the southern Cascade Range in maximum germinability. northern California were collected biweekly in 1967. Many cone and seed characteristics were observed Collections began on August 15 and ended October in an attempt to find a simple, effective index of cone 9–3 days before seed fall began. Cone specific gravity and seed ripeness. Specific gravity was significantly and several other cone and seed characteristics were correlated with nearly all measures of seed germina­ measured for each collection, and seed germination tion in both firs. Results indicate that white fir cones was tested on both freshly harvested and stratified can be collected when cones average about 0.96 spe­ seeds. cific gravity–a point reached about 3½ weeks before White fir and red fir cone specific gravities were seed fall began. A firm recommendation is more dif­ similar in pattern. Both held nearly constant until ficult to make for collecting red fir cones. Unlike that mid-September, but then dropped rapidly until seed of white fir, red fir seed germinability continued to fall began on October 12. In contrast, white fir and increase up to the beginning of seed fall. Nevertheless, red fir seed germinability exhibited different patterns. we may conclude that red fir cones should not be There was little difference in pattern, however, be­ picked if their average specific gravity exceeds tween freshly harvested and stratified seeds of the 0.75–reached about 2 weeks before seed fall began in same species. No seeds of either species germinated this study. To obtain a reliable estimate of average from cones collected in mid-August. White fir seed cone specific gravity at least three cones from each of germinability increased rapidly in collections made up four trees should be measured. to mid-September and then tended to level off. Red A method combining several seed characteristics fir seed germinability, however, tended to increase seems more direct and simpler than using cone spe­ steadily for collections made up to the beginning of cific gravity as an index of seed maturity. White and seed fall. In both firs, stratifying seeds affected germi­ red fir cones should be ready for harvest when nation capacity very little, but increased germination 1. Seed wings are uniformly brown with a deep rate profoundly. magenta edge. In 1968, biweekly cone collections were repeated 2. Seeds are free or only loosely attached to cone in red fir and the vigor of red fir seedlings from strati­ scale. fied seed was tested. Both ovendry weight and pro­ 3. Embryos are uniformly pale yellow-green. portion of healthy seedlings increased significantly 4. Embryos entirely fill embryo cavities. until mid-September, and then nonsignificantly until The ratio of embryo length to the length of the seed fall began on October 8. embryo cavity was the single most useful index of A limited test of artificially ripening white fir seed maturity found. Future studies should aim seeds was successful. Cones collected in mid- towards verifying this characteristic as a seed ma­ September–4 weeks before seed fall–and stored in a turity index for all conifers. 1 he demand for white fir (Abies concolor Gord. with extreme care, especially when cones are col­ & Glend.) and red fir (A. magnifica A. Murr) lected on logging operations or on any down trees. To T seeds increases each year in response to increas­ help solve this problem, forestry research must deter­ ing demands for planting stock. Often, forest nur­ mine when acceptable seed viability is reached in the series cannot fill all requests for true fir seedlings. maturing cone, and find some easily measured charac­ Low viability of the seed is a major problem. teristics of the cone or seed that indicate this point. Lanquist (1946) concluded that the relatively low This paper explores the usefulness of cone specific germination he found in these two species probably gravity and several other cone and seed characteristics was the result of seed immaturity. He warned that as maturity indices of white and red fir seeds, and germinative capacity of seed is so vitally affected by reports a limited test of artificial ripening of white fir time of cone harvest that this time must be selected cones. METHODS Seeds tested in 1967 came from six white and tion. Therefore, at each collection (1967) half the eight red fir trees in a mixed stand at 6,000 feet cones in each specific gravity class were broken open, elevation on the Latour State Forest. The Forest lies and the seeds were removed by hand. All insect- on the west slope of the Cascade Range, 37 miles east infested, broken, and aborted seeds were discarded; of Redding, California. The trees were vigorous, full- only seeds that appeared sound were kept for testing. crowned specimens ranging from 48 to 92 years of Germination testing was begun within 24 hours of age and from 14 to 28 inches d.b.h. collection on four 100-seed samples of each specific At least four cones were collected at random from gravity class. The seeds were kept moist during ex­ each tree. Five biweekly collections began on August traction and cleaning to prevent the possibility of in­ 15 for red fir and on August 17 for white fir. The last ducing dormancy through drying of the seed coat collection was on October 9 for both species–3 days (Kozlowski 1971). The samples were placed on a before seed fall began. moist medium of two parts vermiculite and three In 1968, some tests were repeated on red fir be­ parts sand in petri dishes placed in a darkened room cause five of the eight sample trees had good repeat held at 24 degrees C. for 100 days. cone crops. Four nearby trees of similar size and age At the end of the 100-day germination period for with abundant cones were selected for additional each collection date, I attempted to determine the sampling. This time cones were collected at four bi­ number of filled seeds in the ungerminated re­ weekly intervals beginning on August 23 and ending mainder. But many seeds had been destroyed by September 30–8 days before red fir began casting molds during the long germination test, and dis­ seed. tinguishing between originally filled and empty seeds At each collection, cones of each species were was difficult. Therefore, germination results are pre­ sealed in plastic bags immediately, and specific