Now is the Time to Winter Sow

After a hectic year of non-stop landscaping work, I have some time on my hands and discovered ‘winter sowing’. I started doing it last winter in a small way with Bells of Ireland and was so successful, that I am winter sowing in a big way this January and February to save my precious time in the spring. Why wait until spring to sow seeds when I can do it right now?

What is Winter Sowing?

Winter Sowing sounds contrary to the practice of starting seeds in a controlled warm, moist environment, but it really makes sense. Many of my seeds, like larkspur, love in a mist (nigella), and poppies, I always seeded outside in the ground in January as they need about 6 weeks of cold temperatures to germinate.

But winter sowing just means that you are sowing seeds outside in the winter elements in closed containers, instead of doing it in the controlled conditions of indoors. The huge advantage of winter sowing for me, is I can do it when I have the time. Also, the seeds are outside, not indoors taking up room in my greenhouse or house, needing constant attention to watering and light requirements. And we aren’t just talking about flowers. Vegetables and herbs fall into the winter sow category too.

Materials for Winter Sowing

I have saved up my plastic containers and have asked friends and neighbors for their contributions so am amassing plenty of containers. Many winter sowers use plastic milk jugs but I don’t use milk in any great quantity, so have used what I have, namely take out containers, fresh produce clamshells, and even plastic crates which I have an abundance of from bulb orders. All you need are a lot of containers that you would normally throw in your recycling bin – milk jugs, juice containers, dollar store finds, cold cut trays, carryout trays, and greens clamshells, like lettuce or spinach containers from the grocery store.

I have started a few seed containers every day and the enclosed seeded trays are outside right now covered under a thin layer of snow. No sprouting is visible this soon, but give it a few months! I am going to ignore them in the meantime. Rain and snow should take care of any watering needs.

No special equipment is needed –  no grow lights, seedling trays, heat mats, and the most important for indoor sowing – space! You can start as early as the Winter Solstice, December 21 and continue through March and even into April. The only trick is to choose annuals that are ‘cold hardy’ and the varieties that you can start this way is staggering (list below).

What Seeds Will Work?

What constitutes a ‘cold hardy annual’? Those are plants that complete their lifecycle in just one year and which can tolerate a light frost. They germinate, mature, produce, and die within a 12-month period, but won’t resprout. Instead, they set seed for the following year’s new generation and can sprout in place, without the need to germinate indoors. Heat lovers, like tomatoes, cucumbers, sunflowers, zinnias, and corn, are not good candidates.

According to the Burpee website: “When you’re selecting flowers for winter sowing, look for seeds labeled with terms like “cold tolerant,” “cold hardy,” “cool season,” “sow in autumn” or “sow in early spring” for successful planting”. These are key words that signal the annual is a good candidate for winter sowing. For the Burpee article on winter sowing, go to When to Sow Seeds For Winter Flowers. 

Some examples include snapdragon, bee balm, poppies, and delphinium; and that’s just the tip of the iceberg. There are so many options to try. If you notice that things are reseeding and coming up in the spring without you doing anything, like cilantro, love in a mist, calendulas, nicotiana, kale, and annual poppies -to name just a few – these are good candidates to winter sow. I don’t depend on them to come up every time in the garden, so to make sure, I winter sow them to ensure that I have them for the next growing season.

Easy Steps to Winter Sowing:

1. Choose seeds from plants that are “cold hardy” (listed below)

2. Save plastic containers, such as milk jugs, soda bottles, lettuce “clamshell” containers, deep foil pans with clear lids, etc. Tall containers such as milk jugs will need to be cut into 2 pieces, so you can access the bottom. Clear or cloudy tops or lids are important to let light in.

3. Poke drainage holes in the bottom of the container and the lid.

4. Fill the container with potting soil, wet it, and sprinkle seeds on the potting soil. Press seeds into the soil.

5. Put the lid on and secure with duct tape or rubber bands. Make sure there are vents for air to escape and rain/snow to enter.

6. Label everything! You will forget what you sowed, so use a waterproof pen on a plastic label or write it on duct tape.

7. Place the containers in your backyard where they receive sunlight, but can’t blow away… and wait until spring!

Care & Feeding of Your Plants – Practically None!

All you are creating are mini-greenhouses that provide the right conditions for your seeds to germinate. The freeze-thaw cycle breaks down the seed coating so that the seed can sprout at the right time. As the seedlings grow, you might need to vent them more, as they need to stay cool. Don’t let them fry in the container when the weather is balmy and sunny. And when they touch the top of the cover, remove to give the seedlings room to grow. By that time, it will be April.

Benefits of Winter Sowing

1. It’s easy
2. Frees up windowsill space in your home and greenhouse
3. You can do it at your own pace in January or February; there is no need to check frost dates for your seedlings
4. It’s cheap, requiring no special equipment
5. Damping off, which is the nemesis of many seed starters, is not a problem with cold temps
6. No hardening off (acclimating them to outside temps)
7. No need to water as rain and snow do it for me!

Winter sowing is also a great way to use up old or questionable seeds. You have nothing to lose by sowing these odds and ends, so you might as well give them a chance. Your seeds will germinate when the first bulbs start to emerge, like daffodils and tulips, and should have great root systems when the weather turns warmer.

Seeds Suitable for Winter Sowing

1. Amni (Queen Anne’s Lace)
2. Asian Greens
3. Bachelor Buttons
4. Beets
5. Bells of Ireland
6. Black-Eyed Susan
7. Bok Choy
8. Broccoli
9. Brussels Sprouts
10. Bupleurum
11. Calendula
12. Cauliflower
13. Canterbury Bells
14. Chinese Forget me not
15. Cilantro
16. Corn Cockle
17. Delphinium
18. Dara
19. Feverfew
20. Foxglove
21. Godetia
22. Larkspur
23. Lettuce
24. Love in a mist
25. Kale
26. Monarda Lambada (Bee Balm)
27. Money Plant
28. Onions
29. Oregano
30. Orlaya
31. Pansy
32. Perennial Flowers
33. Petunias
34. Poppy
35. Radish
36. Sage
37. Scabiosa
38. Snapdragon
39. Spinach
40. Sweet pea
41. Sweet William
42. Thyme
43. Yarrow

Final Tips

It is important to sow thinly so you aren’t germinating mats of seedlings. It is hard to separate balls of intertwined seedlings without damaging them. It is better to cut them into blocks and plant the entire chunk of plants. Larkspur especially hates to have their roots tampered with, so sow these very thinly in your container and transplant them to their permanent location when young, no more than 2 – 3 inches high.

For my blog post on cold-hardy annuals, go to Top 10 Annuals That Can Take the Cold.

For a great article on the pros and cons on winter sowing, go to Growing With Plants.