Editor's note: This is the second in a two-part series of starting plants from seed. This week covers sowing seeds outdoors in winter.
In nature, moisture, temperature and daylight dictate when seeds germinate. All plants produce seeds that grow on their own the following season (or in later seasons) as conditions become suitable. Planting now allows seeds to germinate on their own when conditions are right and produces plants that are already adapted to the outdoor environment.
Seeds vary with the variety of plant, each needing different amounts of cold and/or moisture to stimulate germination. For more consistent results than nature itself provides, use a cold frame to start your seeds or create a miniature greenhouse with a recycled container.
You can use about any kind of plastic container to start seeds, as long as light can get through the top. Common choices for winter sowing are empty milk jugs, 2-liter bottles or even foil cake pans with clear plastic lids. If you use a milk jug or bottle, cut it open 5-6 inches from the bottom so that you can easily plant in the bottom portion. You should also make a few holes or slices in the very bottom to allow excess moisture to drain, like the holes in the bottom of a flower pot.
Choose a lightweight potting soil for your planting project. Topsoil and garden soil may hold too much water and cause the seed to rot before germination.
Fill the bottom of the container with approximately 3 inches of the potting soil and lay the seeds right on top. Small diameter seeds may not need to be covered with soil - simply pat the soil surface with your hand to make sure the seeds are firmly contacting the soil. Cover larger seeds with potting soil until they are covered to the recommended depth.
Once the seeds are planted, water thoroughly, taking care not to wash the seeds out of the new planter. Replace the lid of a flat container, or if you used a bottle or jug, tape the top of the container back to the base. Remember that the container will be sitting outside, so you will need to use freezer tape or duct tape that can withstand temperature extremes. Toss (or recycle) caps to bottles and jugs.
If you don't see plants right away, don't worry - the seeds will germinate when the time is right. New plants are ready to transplant after the first true leaves emerge. Open the container and break the seedlings apart. If the plants are small and close together, break into chunks about the size of a quarter. Roots are easily damaged when trying to completely separate tiny plants and the seedlings will thin themselves as they mature.
Warm days can literally cook the plants in their containers, so make sure to transplant the seedlings before temperatures get too high.
This method of starting seeds allows you to get a lot of plants without investing much money. You can possibly even get the seeds for free; winter sowing enthusiasts share seeds through plant swaps and online seed exchanges. Remember that seeds of hybrid varieties are likely to be different than the plant they came from or not viable at all, and be aware of and avoid species that are invasive in your area.
Special thanks to Douglas County Extension Master Gardener Jan Butin, who shared her expertise on this subject. Jan winter sows seeds of her own and gives educational talks on the subject as part of the Douglas County Master Gardeners Speaker's Bureau.