Many people like to try their hand at seed germination but shy away from tree seed because they are unsure when the seed ripens and what exactly to collect. Tree seeds from the black walnut and oak are obvious, but others such as fir and pine are more subtle in appearance. Tree seeds consist of three general types -- dry fruits that release their seeds at maturity like cottonwood; dry fruits, usually one-seeded, that are separated from the plant without releasing their seeds like maple and oak; and fleshy fruits that drop with their seeds enclosed like Russian olive and hawthorn.
The majority of tree seeds will not germinate immediately after dispersal from the tree. Many seeds are not mature enough physiologically to germinate or certain inhibitors may be present. Another type of dormancy is physical dormancy such as a hard impermeable seedcoat. These dormancies are protective mechanisms for the plant that prevent death. If the seeds germinated immediately, most seedlings would not survive the weather extremes of our climate. Methods used to break dormancy in seeds include stratification and scarification. Stratification uses low temperatures and moisture to duplicate natural conditions. Scarification uses mechanical abrasion, heat, or acid treatment to modify the seedcoat. In many cases a combination of methods are used. Seed viability of tree species varies from a few weeks to several years.
Specifics on seed collection will follow in the next newsletter.
This article originally appeared in the August 12, 1992 issue, p. 138.