Planting Seeds in Winter and Cold Stratification

It surprised me when I stopped hating winter. Now, don’t get me wrong, I can’t stop dancing when it’s warm and bright out, but I have come to appreciate and even love that there is a certain magic happening during winter.

As a beginner gardener, I started dreaming of spring as soon as the holidays were over. As I became more interested in growing things, this time of dreaming turned into planning, and as I became more experienced, a time of planting!

Winter Harvest 

Be like Mother Nature

Mother Nature is a masterful teacher. So much of what we try to create in our gardens are just shadows of what she does perfectly herself. When we plant certain types of seeds in mid-winter, we are taking advantage of the cold and wet conditions to help break the dormancy of the seeds for us, for easy germination come spring. This process is called cold stratification. We can recreate this in controlled conditions by mixing our seeds with barely damp sand, vermiculite, or peat moss and putting the damp seed mixture in a container in the refrigerator. But why go to all this trouble when nature is ready and willing to help out?

There are generally two reasons seeds could benefit from cold stratification. The seeds of some species go into a period of embryonic dormancy and often will not sprout, or will have a poor germination percentage, until this dormancy is broken. Other species have seeds with a very hard seed coat, and exposure to the moist cold helps break down this shell for easier germination in spring. Sometimes you will find that both apply. When we let Mother Nature do the work for us, the cold and moist of winter triggers the seed's growth and subsequent expansion, eventually breaking through the softened seed coat in its search for sun and nutrients. The time needed to stratify seeds depends on species and conditions, though in many cases two months (8 weeks) is sufficient.

What kind of seeds can be sown outside in winter?

Once you know what to look for, it’s easy to plan. On your seed packets, look for the term "cold stratification". Often, perennials and self-sowing annuals can sprout after being sown in winter, but if they are not species that require stratification, it's probably a better bet to wait and sow them in spring or start then indoors. If you are unsure, you can always try and sow a few seeds from your packets and see how they come up for you come spring.

When is the best time to sow winter seeds?

This answer depends on where you live, but a good rule of thumb is to wait until winter temperatures are here to stay. Folk wisdom for centuries has suggested that the Winter Solstice is a good time, and while that sounds charming, my experience has been mixed with that date. Here in Asheville, (zone 7a, 7b) it is usually still too warm for good results. The risk here is if you sow too soon, the warmer soil temperatures can break down the seed coat too quickly, and give spotty germination come spring. The sooner you plant the more chance you have of a critter looking for food making a meal of your investment. January or early February is my favorite time to plant for stratification. It gives me the required 8 weeks, and it is consistently cold enough at that time that I don’t worry as much.

What are the best ways to sow seeds in winter?

There are two fantastic options for this. The first is just direct sowing in the ground right where you want them to be. This couldn’t be easier, just clear the soil and scratch in where you want your plants to be, and spread a half inch or more of straw on top. It’s an excellent idea to write down in your garden journal where you planted and on what date, and if you want to be very thorough, place a plant marker in the soil where you planted. I use this method a lot, both because it’s super easy, and because I am a fan of all things easy.

The second way is similar, but more controlled, which makes it a great option for seeds that are expensive, rare, or otherwise special to you. In this case you will sow your seeds in pots, which will allow you to maintain more control over the seeds and their environment, and if needed you can baby them through their infancy until they are strong enough to transfer into your gardens. If planting in pots, I still recommend keeping the pots on the ground, and if possible in a sheltered location for protection. And don’t forget to water! The point of cold stratification is to keep the seeds cold and moist, so if you let your seeds dry out too much, you will not get the best germination results.

What specific varieties of seeds should I sow in winter?

Herbs

Anise Hyssop, Catnip, Clary Sage, Lavender, Lovage, Mullein, Nettle, St. John's Wort, Valerian, Yarrow.

White Yarrow

Flowers

Black Eyed Susan, Columbine, Coreopsis, Echinacea (Purple Coneflower, and Tennessee Purple Coneflower) Flower Mixes, Lupine, Milkweed (except tropical varieties Bloodflower and Balloon), Money Plant, Corn Poppy, Hungarian Blue Breadseed Poppy, Oriental Poppy, Sochan.

Purple Coneflower Echinacea 

	Article Written by: Angie Lavezzo
	About the Author: Angie Lavezzo is the former general manager of Sow True Seed. Beyond her professional role at Sow True, Angie's passion for gardening extends into personal hands-on experience, fostering plants and reaping bountiful harvests.