Winter sowing is a technique used to propagate certain trees and shrubs, as well as some annuals, perennials, and vegetables. It involves sowing seeds of these plants outdoors in the autumn or winter, instead of in the spring – much like Mother Nature would if the seeds were left to drop naturally.
Many shrub and tree seeds require a period of cold to break dormancy and germinate. Known as stratification, this period of cold is often artificially induced by placing the seeds in a freezer or refrigerator before planting them, but when seeds are winter sown in colder climates, the appropriate stratification period happens naturally.
The benefits of winter sowing are many.
What trees and shrubs respond best to winter sowing?
The seeds of tropical plants, tender annuals, and frost-sensitive species are not good candidates for winter sowing, but many cold-hardy trees and shrubs are. Look first to native species that grow well from seed; these are almost always good candidates for winter sowing. Seeds collected from a hybrid trees or shrubs may not result in a plant that’s identical to the parent. For the best results, winter sow seeds of straight species, instead of hybrids.
A few trees and shrubs that perform well when winter sown include:
Learn how to winter sow.
To winter sow, simply bury several tree seeds or shrub seeds of the same variety in a Root Control Bag filled with the potting soil/compost blend. Typically, a depth of one-and-a-half-times the height of the seed itself is best. Space the seeds a few inches apart, and label the container so you know what’s planted in it. Water the seeds in, and put the pot in a sheltered site, if possible.
If you start seeds of perennials, annuals, or other non-woody plants via winter sowing, you’ll also need to cover the tops of the container with a cloche of some type for added protection. A layer of clear plastic will suffice. Shrub and tree seeds do not typically need this extra insulation, though tossing a handful of straw or shredded leaves on top of the pot helps insulate the seeds.
Come spring, the germination of plants will take place when the seeds are ready. The seedlings can then be separated and re-potted, or planted in the ground as soon as they reach a few inches in height.
Potential problems with winter sowing.
Occasionally rodents or birds may dig up your seeds during the winter. To keep this from happening, pots can be topped with a layer of protective hardware cloth. Just be sure to remove it in the spring, before the seeds germinate and grow up through it.
If natural precipitation doesn’t occur, you’ll have to irrigate your pots occasionally throughout the winter, but don’t keep them overly wet or the seeds may rot.
Winter sowing is a great way to propagate trees and shrubs. It’s smart, simple, and fun!