Germination of Tree Seeds
by: Richard Jauron, Department of Horticulture Iowa State University.
Growing trees from seed can be fun. However, the seed of most tree species won't germinate immediately when planted because they are in a dormant state. Dormancy must be broken before the seed can germinate.
In some tree species, dormancy is the result of a thick, hard seed coat. The seed coat may be broken in a variety of ways and the process is referred to as scarification
. Mechanical means, such as a metal file or coarse sandpaper, can be used to break the seed coat. Treatment with boiling water has also been successful for a number of tree species. In nature, the seed coat may be broken by microbial action, passage of the seed through the digestive tract of a bird or other animal, exposure to alternate freezing and thawing, or fire.
The seed of many tree species will not germinate until they have been exposed to cool temperatures and moist conditions for several weeks or months. Winter weather in Iowa provides the necessary conditions to break dormancy. Gardeners can accomplish the same results by a process called stratification
. Tree seed can be stratified by placing the seed in a moist 50:50 mixture of sand and peat moss. Suitable containers include coffee cans, plastic jars, and cottage cheese containers. (Punch holes in the lid of the container to provide air.) Seed can also be stratified in plastic bags. Stratify the seed in the refrigerator.
The seed of some trees, such as redbud, have hard impermeable seed coats and dormant embryos. They require both scarification and stratification for germination.
Specific information on collecting and planting seed from several tree species are at the
edit to add:
Most seed packets provide germination and cultural information for the crop. Oftentimes, however, the information is rather brief. For many home gardeners, a reference book with more detailed information is an indispensable resource.
The "Ball Culture Guide: The Encyclopedia of Seed Germination"
by Jim Nau is an excellent book
for home gardeners and commercial growers. The book provides germination temperatures, light requirements, germination times, growing temperatures, and crop times for over 300 seed-grown crops. These crops include annuals, perennials, vegetables, and ornamental grasses.
"Burpee Seed Starter: A Guide to Growing Flower, Vegetable, and Herb Seeds Indoors and Outdoors"
by Maureen Heffernan is another helpful book.