Longevity of Ponderosa Pine Seed

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Seed of ponderosa pine (Pin-us ponderosa Laws.) collected in northern Arizona from 1909 to 1960 was tested for germination in the winter of 1960-61. Even after 35 years in storage, 16% of the seeds germinated. Various authors have stressed the importance of low moisture content and low air temperature for successful storage of conifer seed. Allen (1957) found that seeds of 11 different conifers can be stored successfully for periods of five to seven years in sealed jars at 00 F. and 320 F. and moisture contents under 10%. Seeds of most species stored at fluctuating room temperature lost viability completely after seven years. Germination of seed of ponderosa pine, however, dropped to only 35% from an initial germination of 66%. Ponderosa pine seed maintained viability when stored 23 years in a cool cellar (U.S. Forest Service, 1944). Storage temperatures slightly above freezing and seed moisture less than 10% are recommended for most species of pine. In this test seeds collected before 1959 were stored in glass jars in a cool root cellar until 1958 when the cellar was converted. to other use. The seeds were then moved to a house. Maximum air temperature of the root cellar is estimated to be between 50? F. and 60? F., while air temperature in the house probably reached Q0' F. during the summer. Seeds collected in 1959 and 1960 were stored in jars in a refrigerator. Standard germination tests (U.S. Forest Service, 1944) were run with a 400-seed sample from each year. Germinated seeds were counted each day and then removed from the flats. Average maximum and minimum air temperatures during the test were 800 F. and 68? F., respectively. The percentage of filled seeds was determined by smashing a 400-seed sample from each year's lot except 1909 for which only 100 seeds were available and 1948 for which no extra seeds were available. Moisture content was determined by ovendrying 10 g to 20 g samples of seed from each lot. Samples from each year except 1909 and 1921 contained viable seeds (Table I). Ninety-seven percent of the seeds collected in 1960 germinated. Germination of some older seeds was 70% after 10 years, 36% after 27 years, and 16% after 35 years. Eighty to 99% of viable seeds in all lots germinated within 20 days. The percentage of filled seeds ranged from 71 to 99. Moisture content was less than 10% for all lots except the one collected in 1959. Ponderosa pine seeds may be kept for long periods in