Winter sowing is a way to start seeds outdoors in a small container greenhouse while it is still winter. Since the most common containers are used milk jugs, it also sometimes is referred to as milk jug sowing. It was first invented by Trudi Davidoff. It sounds so good that one wonders if it can be true. Well, you will never know if you do not try it, so we did.
I did not doubt the system, it sure sounds possible, seeds will germinate whenever it is naturally time for them. In zone 3, however, that time might come way too late. Still, we did try it out, and here are our first results.
After our experience with winter sowing in zone 3, we updated this blog post with detailed instructions.
Why winter sowing
Winter sowing is a great way to start seeds without a growing room, grow lights, or a greenhouse. If you have no optimal conditions indoors for seed starting, consider winter sowing.
For winter sowing we use recycled containers (gallon jugs), reducing the cost and plastic needed for seed starting.
Winter sowing makes seed starting easy, less care, and less work with hardening off plants. However, some care and hardening off are needed here too.
If you do it right, winter sowing produces more robust seedlings. Especially perennial plants and cold-hardy plants do well in winter sowing.
What seeds to start in winter sowing
Winter sowing does not have any magic to it. What we do here is create a somehow sheltered environment to let seeds germinate whenever the conditions for that seed are right.
So if a plant variety germinates under cooler conditions, that seed will germinate earlier. If a plant variety needs warm soil to grow, that seed will germinate later accordingly.
In a more temperate climate, any seeds can be started in winter sowing. They will germinate and start growing whenever the conditions in the little container greenhouse are suitable.
In zone 3 however, only cold-hardy seeds germinate on time to make it worth it. The little container greenhouse is not able to create an environment for heat-loving plants if the outdoor temperature is too cold.
If you still want to start all seeds with winter sowing, that is possible with a bit more care. We will talk about it later.
When to start winter sowing in zone 3
The whole idea of winter sowing is that it can be done in the middle of winter and it will work. This is true for a tempered climate. Any seed that would naturally survive being frozen and then germinate after that, would work for winter sowing in zone 3 too.
We have all seen hollyhocks, dill, cilantro, and more come up in spring after a long cold winter. Winter sowing is the same idea, just more controlled, and since we create a little microclimate, the seeds will come up a bit earlier.
With that being said, -40 degrees are hard on the containers and may cause damage to some seeds. There is no need to expose them to it. The seeds will not come up any earlier if we start them in winter sowing earlier. They will come up when the soil reaches a minimum temperature.
In my first experiment, I waited till March, and that was plenty of time. If you want to start hardy perennials, mid to end February seems to be good timing.
In winter sowing we are aiming for young, healthy seedlings. For the most part in zone 3, it seems to be a good idea to go with the same seed starting schedule we use for indoor seed starting. You can find a free printable schedule here.
Preparing the container greenhouse
Any translucent containers can be used for winter sowing, the most common ones are 1-gallon jugs.
In a clean container, make 10-12 holes at the bottom and lower sides for drainage.
Now cut the jug just below the handle, leaving 1-2 inches by the handle, so that the top can be closed and opened. You want to have enough room for the roots to grow.
Fill the container with light, well-draining soil. Do not use seed starter soil, it usually has no nutrients in it. Use for example Promix organic veg and herb mix soil for starting seeds.
Or if you use a soil mix that has no fertilizer in it (read the labels) simply mix in compost about 1/3 by volume. This is important because we will not transplant or water the seedlings regularly as you do with indoor seed starting. The seedlings need some nutrients to be able to grow on their own.
Water the soil throughout, and let it drain. You are ready to plant now.
Planting the container greenhouse
Plant the seeds as usually reading the label of the seed package. Most seeds need to be planted about 3 times their size deep.
If using very small seeds, just sprinkle them on top and cover lightly with some soil. Push the soil down lightly to make sure the seeds are in contact with the soil.
Do not overplant. Keep in mind, that these seedlings will be in the container till it is time to plant them in the garden. Generally, they will be smaller than your usual seedlings started indoors. They still need some space to grow healthy roots.
Label the container so you know what is inside. Labeling also inside the container seems to work well since the outer surface will be exposed to the elements for months. Use a marker that will last.
After planting close the jugs and seal them with duct tape. We want to be able to keep all the moisture in and have no wind or airflow in the container. Only the lid is left open.
Bring the winter sowing container outside
Now it is time for the winter part of the sowing system. In our first experiment, we placed the containers on the south side of our house. A few days later we got snow, and some more snow and heavy frost. Too cold for my liking. But I wanted to try the winter sowing in zone 3, so we did not pamper the seedlings at all.
I also had all the containers in a water-tight box, which I would not recommend.
Instead, bring the containers out into the garden to a snowy location. If you can, give them a sunny, but somewhat sheltered location from the wind. Place them into the snow, so the snow gives some temperature stability and insulation.
If there is no snow and the night and day temperature fluctuates a lot, you can either cover the containers for the night with a protective blanket or bring them in. This will help to speed up germination and protect young seedlings. Especially if you are trying to start warm weather seeds, protecting them a bit more is a must.
Frankie-Lou Fuller who loves winter sowing in zone 3 has another great tip for a no snow situation: Make a protective wall all around the container greenhouses with containers that are filled halfway with water. It helps keep the temperature somewhat more stable, not totally exposed during the nights, and overheat during the day.
Seedlings care in winter sowing
Once the seedlings are up and growing they do need some care. Now, in my trial, I did not do anything except rescue them a couple of times from drowning. If you do not keep them in a trey, that will not happen.
As the seedlings grow, they will need water. You will know if they need water by lifting the containers. A dry container will feel very light.
Watering from above is not a good idea. Instead water from below by placing the jugs for a few minutes into a tray with water.
As we mentioned above, protect the containers from extreme temperatures. The winter sowed seedlings will be pretty hardy, but if you are growing a frost-sensitive plant, and a sudden deep freeze is coming, bringing them indoors is a good idea.
Also, later in the season overheating might be an issue. Spring sun can be very intense. After the snow is melted, a location with some protection from the afternoon sun is a good idea for the growing seedlings.
Hardening off plants in winter sowing
The plants in a milk jug container are not used to direct sunlight or air movement. If you leave them closed for too long, they might be very weak seedlings.
About a week before planting the seedlings out into the garden, open the containers. Start that process in a shady, sheltered location. Slowly introduce them to sunlight and wind. Covering at first with fleece is a good idea. After that, they are ready to be planted and grow into healthy plants.
If you want to learn more about winter gardening, here are some inspiring books:
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We winter sowed a couple years ago and it was great. I wish we would have doe it this year 🙁 It was too cold to even go outside most days. I am so glad it is over!!
Yes this is a cold winter, and a cold spring so far. Maybe not the best year for me to try winter sowing. Glad to hear it worked for you in the past.
I have been doing this for a few years now and have always had GREAT success!! My only problem is that I usually don’t put them out until the end of March just because I don’t get my butt in gear! I learned it from a gardening class and she recommended to do it in mid to late February. I do a lot of tomatoes and peppers and I swear I have had every seed germinate. I am also in zone 3, by the way.
Thank you for sharing Becky! This is very interesting. I only start winter crops, not tomatoes and peppers. I am afraid they would freeze. Great to hear that it works for them too.
I am a huge advocate for winter sowing. I’ve had great luck here in zone 5. Neat tip from my husband (while watching me chop up milk cartons with a paring knife): Fill the cartons with water and let it freeze outside, then cut and drill. It’s much more stable a surface to work with.
That is a great tip, thank you Jessica! Great to hear also that it works in Zine 5. We will see how it is in Zone 3.
No experience with this type of planting for me….I have not heard of this kind. Let us know how the turn out!
I heard about it the first time this winter, so it is new to me to. Will keep you posted.
Great advice Anna – I don’t have that kind of winter, but it’s interesting to learn 🙂
My winter sowing has been a huge success for the most part. I learned this method from your previous blog post about it a few months ago. I did my first sowing in early Feb. I am now just waiting to be able to put some plants into the ground and into outdoor pots. We had snow and ice but those milk jug’s kept the plants growing, will definitely utilize this method again.
Oh good to hear! Lets hope it works good for me too. It sure would be good, such an easy way to start seeds.
I hope to get some pictures posted soon as a follow up to the blog post I did about it. Some of our tomatoes FINALLY sprouted in the last few days. It took them about 3 weeks.
Looking forward to see them.
Interesting! I would have never thought that these would grow in the midst of so much snow…but I don’t know much about snow LOL I’m interested to see how this works out!
Well, we will see. Hopefully I can see some green in there sometimes soon 🙂
We’re not as far north as you are so, good on ya!!! We can usually get by with planting cold sturdy crops and using hort fabric or a hoophouse/cold frame set up. I like the simplicity of recycled materials, though. In fact, I just killed my Swiss chard transplants because I failed to do something similar during our surprise (ha! I knew it was coming in my bones!) snow and they keeled over. All my fancy garden stuff is packed for our move. Ah, well – that’s how it goes!
We all learn through trial and error, don’t we.
I do this successfully in Can zone 4. I don’t think the winter cold makes much difference as the seeds stay dormant until conditions improve. In fact, I always make sure it’s not a warm spell when I set them out so they don’t break dormancy long before their time. Not every seed germinates, and some things never germinate at all, so I would never use precious seeds this way, but it’s a great way to get very sturdy young plants quite early in the season. I use Trudi’s hunk o’ seedlings method (sow thickly, then break off a “hunk” off seedlings instead of separating individual plants) and it works very well to get lush growth quickly in the garden.
Thank you for sharing, Bev! So if my seeds do not germinate, it might be because I did not plant enough of them. Well we will see.
Living in zone 8, I don’t have to be concerned about winter sowing, but I do love to read about it and to see the pictures. I learn so much from your posts!
Thank you Alli! I so appreciate faithful readers no matter from what growing zone!
Can you describe what you were sowing? I am in the same zone and would love to try this next winter!
Cabbage, broccoli and swiss chard germinated the best. Dill, salad and celery did ok. So the hardier the plant, the better it works. I really liked it. Happy gardening!
Thanks for the info on winter sowing. I live in zone 2 in interior Alaska and will definitely try this this spring. One question: what do you mean when you say to duct tape the containers closed? Also, do you think it is rougher for the seedlings to be in a greenhouse where they will get warm day time temps and potentially subzero night temps (as compared to being outdoors in beds or containers)?
Jenny thank you for your questions. Duct tape the containers so they stay closed so wind and snow cant get to the plants. Just a tape all around the cut. Does that make sense?
I am not sure on the greenhouse. I could imagine it would be harder on the seedlings to be in the greenhouse. Maybe just use the greenhouse as an extra shelter for especially cold times (blizzards), we get does even in spring.
I want to know that too, because hubby built me a 6×10 greenhouse to start seedlings in and I am itching to get started, so I’m thinking of winter sowing. I winter-sowed a bunch of stuff a few years ago (zone 3) and it was my best gardening year ever. I’m just concerned about the heat factor in the greenhouse, which is placed strategically to catch as much sunlight and warmth as possible. I am also wondering if I do winter saw in the greenhouse if I could dispense with the jugs and just put regular seedling pots out. 🙂
I have started seeds in the greenhouse as early as March, direct in the ground. So starting them in pots with a cover for protection should work great. I just never have, since I also have the option of the indoor sunroom.
I’m also trying this method in zone 3 this year.
I had a setback – I put my jugs on a bench and they got blown over a few days ago. I’ve resettled the dirt and moved them to amore sheltered spot…but I have no idea if anything will germinate.
A friend just shared with me, she has hers in her basement, they grow quicker this way. I thought it was a great way to trick our Alberta weather ;).
In the winter-sowed garden I did a few years ago LOTS of stuff blew over and they still produced fine. 🙂
It is amazing how hardy those plants are, right. Glad it worked so well.
Winter sowing is on my list of things to try. I do a variation of this by planting cold hardy seeds in my greenhouse around the end of February.
It is a great way to start seeds if you do not have indoor room for seed starting. I have never started that early in a greenhouse. Happy it works for you.