It’s December and gardening is likely pretty far down the list of things you’re thinking about right now — but you might want to reconsider. If you are interested in growing plants from seed, a little effort expended now will pay huge dividends in spring. Winter sowing is a method developed by plant gurau Trudi Davidson that allows you to take advantage of plants’ natural seed growth cycles in a sustainable, controlled way. Most vegetable and non-hardy plants can be winter sown in February or March, but now is the perfect time to get perennial flowers and native plants started.
To begin, collect recyclable containers, then clean and sterilize them by washing them in a 10% bleach solution. Any clear or translucent container will work, but milk jugs are preferred for their size, translucence and availability — but soda bottles or bakery containers will also work. Cut the container open several inches from the bottom, leaving a small section still attached. After poking a couple of holes in the bottom for drainage, add several inches of seed mix potting soil and plant the seeds according to the directions on the package.
Seal the container with duct tape, marking the plant name and sowing date with a grease pencil (markers will fade in sunlight). Allow for air and water to enter the container by leaving the lid off the milk jug, or cut a couple of holes in the top of the container — but not too many or our arid climate will dry out the containers quickly.
Winds can topple your containers, so place them in another box or otherwise secure them. Place them on the north side of your house or anywhere that snow and rain can reach them and provide a water source—for this reason, do not place them inside a shed or other roofed enclosure. Exposing the seeds to the freeze-thaw cycles through the winter helps them grow when temperatures warm.
Once daytime temperatures reach 40-50 degrees, check the containers daily. This is the most vulnerable time for seedlings because they can sprout — and die — quickly if not properly cared for. Once you notice sprouts, make sure the containers remain evenly moist. Expect different plant types to germinate at different times.
Once it’s warm enough and your seedlings are large enough to transplant, you can move them from their cozy container to the planting bed of your choice. Plants grown using this method will not be ready as early in the season as those grown indoors, but they will be stronger and more resilient. This method is especially effective for perennials and native plants.
So curl up with a cozy blanket, browse your favorite plant catalogs and get ready for spring.
To see some of our favorite sources for all types of seeds, visit our blog at http://conservationgardenpark.org/blog.