So, I’ve harvested some of the seed pods and finally decided to google the issue and most sites are recommending refrigerating the seeds at 41degrees F for 6 weeks. Can I freeze them? Should the seeds be in a medium when frozen? Do I need to nick (a la morning glories) the seeds and soak first? So many questions! Thanks!
Thank you for contacting the Toronto Master Gardeners.
The seeds of most tree species will not germinate immediately when planted directly into the ground because the embryos 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 this process is referred to as scarification. Scarification is necessary to allow water and gas exchange within the seed. 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. This is called stratification. Stratification is a method of getting seeds to germinate by providing them with a few weeks of damp, cold conditions. This ensures that the seeds do not germinate before winter conditions set in thus killing the seedling.
In the case of Redbud, the seeds have hard impermeable seed coats and dormant embryos. They require both scarification and stratification for germination.
First you need to collect the redbud pods when they turn brown in late fall, Air dry the pods, then remove the seeds. You can store dried seeds in sealed glass containers in an environment that stays at or below 5C. Store them until you’re ready to plant them; redbud seeds can stay dormant for years.
Redbud seed can be scarified by nicking the seed with a knife or by submerging seed in boiling water for one minute.
Once scarified, place the seed in cool, moist soil for 5-8 weeks. The soil temperature should be around 4C. As with storage, it would be best if you place this growing medium in an area that is able to hold this temperature for the duration.
Good Luck