How Long to Stratify Tree Seeds?

Tree seeds, such as those of Jananese maples, require stratification before planting.

Stratification of seeds by refrigerating them helps promote germination by simulating nature's seasonal changes. Some seeds simply cannot germinate unless they have been subjected to cold temperatures for a specific minimum period of time.

Stratification Times

Stratification of seeds varies in length of time required for the species from a few weeks to months. Tree seeds may require as little as three weeks of stratification while others need as long as 150 days. Some tree seeds, like those of Japanese maple, require a drying period in warm temperatures before stratification.

Time Frame

Seeds collected during the summer or fall can be stratified over winter and planted in spring. Some seeds do not need stratification and should be planted immediately. The tree's natural habitat and native range can help determine when to start stratification.

Natural Stratification

The natural process of cooling and freezing will stratify the seeds in regions where the tree is a native. Seeds planted in a bed or in pots for later transplant and left in the ground stratify naturally over winter to germinate and grow in the spring.

References

• "The Complete Book of Plant Propagation"; Jim Arbury, Richard Bird, Mike Honour, Clive Innes, Mike Salmon; 1997

Resources

• Iowa State University Extension: Germination of Tree Seed