Garden Blog

Planting Seeds in Winter and Cold Stratification

Best herbs, flowers, and vegetables to plant in the winter time!

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!

When we plant in mid-winter, we are taking advantage of the cold and wet conditions to help break down seeds for us, for easy germination come spring.

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 in mid-winter, we are taking advantage of the cold and wet conditions to help break down seeds for us, for easy germination come spring. This process is called cold stratification. We often recreate this in controlled atmospheres 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 types of seeds that benefit from cold stratification, those species whose insides go into a period of embryonic dormancy and often will not sprout, (or will have a poor germination percentage) until this dormancy is broken. The other type is those seeds that have a very hard seed coat, and exposure to the moist cold helps break down the 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 seeds growth and subsequent expansion, eventually breaking through the softened seed coat in its search for sun and nutrients. The time taken 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 in winter?

Once you know what to look for, it’s easy to plan. On your seed packets, look for terms like “self-sowing”, “direct sow outside in early spring (or) fall”, “perennial”, “cold hardy”, or “cold stratification”. Keywords like these are good indicators of seeds that will work well for winter sowing. Generally speaking, perennial seeds, cold weather vegetables and hardy annuals are great options for winter sowing. 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 now. 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 as good germination results as their wetter counterparts.

What specific varieties of seeds can I sow in winter?

This list is a good one, but I’m sure I’m missing some, and we’d love to hear about them in the comments! I should note that with the exception of Asparagus and Spinach –because they germinate better with the cold period, I rarely winter sow my vegetables anymore. It just works for me to sow directly in spring, or start them inside to transplant out, but that’s just me. Experiment! Gardening is an art, and what doesn’t work for me may be perfect for you!

Vegetables

Arugula, Asparagus, Beets, Broccoli, Brussels Sprouts, Cabbage, Carrot, Cauliflower, Collards, Endive, Kale, Kohlrabi, Leeks, Lettuce, Mache, Mustard, Pak Choi, Radicchio, Radish, Rutabaga, Salsify, Spinach, Swiss Chard, Turnip.

Kale is a great winter time green is plant because it is frost tolerant.

Vates, Dwarf Blue Curled Scotch Kale 

Herbs

Anise, Anise Hyssop, Borage, Burdock, Catnip, Chamomile, Chervil, Chives, Cilantro, Clary Sage, Dill, Feverfew, Hyssop, Lavender, Lemon Balm, Lovage, Marjoram, Mullein, Nettle, Oregano, Parsley, Pennyroyal, Sage, Scullcap, Sorrel, St. John’s Wort, Tansy, Thyme, Spilanthes, Valerian, Yarrow.

If you want some herbs in your garden in the winter time chives are frost tolerant and a great winter time herb.

Chives 

Flowers

Bachelor Button, Bee Balm, Black Eyed Susan, Columbine, Coreopsis, Cosmos, Daisy (all varieties), Dianthus, Echinacea, Flower Mixes, Forget-me-not, Gaillardia, Lupine, Marigold (all varieties), Milkweed (all varieties), Money Plant, Morning Glory, Nemophilia, Nigella, Poppy (all varieties), Snapdragon, Sochan, Viola, Zinnia.

The best flowers to plant in the winter time are ones that need to undergo stratification, the process that breaks the hard shell for the seed to germinate.

Purple Coneflower Echinacea 

Written by Sow True Seed General Manager, Angie Lavezzo

6 thoughts on “Planting Seeds in Winter and Cold Stratification

  1. avatar Holly Allen says:

    This is for Aaron Taylor…It’s been awhile since your post. I hope you’ll get this. Winter sowing is a reference to sowing in containers. Such as milk jugs, or clear 2l soda bottles, this creates a mini greenhouse effect. One then sets the jugs out into winter weather. As the proper soil temp is achieved for those seeds they will germinate. Starting advanced plants for later transplanting. This method works well for those who don’t have a greenhouse for baby starts. It has it’s drawbacks, as it isn’t appropriate for root crops, or for plants that don’t transplant well, such as beans. I hope this helps clarify. happy growing!

  2. avatar Edie Koenig says:

    Aaron,
    You said to stratify for 8 weeks but you didn’t say how cold the seeds have to get. I want to stratify in the refrigerator (37%) or freezer (0%) . Which should I use? And should I use a damp medium? I can’t plant out before mid-March at the earliest, so I don’t want the seeds to sprout too early. Here in the Willamette Valley of Oregon, it may or may not get down to freezing again this winter and daytime temps may be in the fifties. Starting in pots and setting outside might work if the seeds don’t have to get any colder than the mid thirties and warmer days don’t cancel the effect. I wouldn’t have to worry about keeping the seeds moist outside as we still have much rain ahead.

  3. avatar Susan S says:

    Great article. Thank you. I’ve been doing this for decades by two methods:
    I watch for plants that naturally come back from the seed they drop in summer or fall (creasy, many flowers, cilantro, lettuce, many herbs, asparagus, onions, etc) and intentionally plant that seed near that time but also save some back for spring just in case.
    I also note what comes up on its own in spring then count back a few weeks and sow. For example, I’ve noticed sunflowers come up around the third week in March so I plant them around March 15th.
    Of course, this is all tempered with the knowledge that most of what I grow is not native to this climate so I have to take that into consideration.

  4. avatar Natalie kramme says:

    Great post! Didn’t realize all the herbs that need stratification. Wish seed companies would put this on their packets. THANKS!

  5. avatar Bianca says:

    Aaron, I’ve seen the same thing—seed packets rarely mention cold stratification. My guess is that they don’t want to scare off the average gardener with instructions that seem too complicated or lengthy, but that’s common sense talking, not any true evidence that that’s what they’re doing.

    In many cases, it may be possible to germinate a seed without cold stratification, but the germination rate is often really, really low. With cold stratification, the germination rate could go from 10 – 20% up to 70 – 80% (or more). I’ve noticed that a lot of these plants have bad reviews on some supplier sites with the complaint that their germination rates are very low, and these are the same suppliers that do not mention cold stratification.

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