I've been trying it in an unheated greenhouse. The results have been mixed. If the new plants can take -3C overnight, they might live. The problem here is the swing from +10 to -10C that frequently occurs well into May. Sowing in jugs will probably delay germination until the worst of the freezing is over. However, once the plants sprout, only the hardy will survive.

Next year I am adding supplemental heat to keep the plants from freezing.

There's also a Canadian WS forum but there too many of the posters are in zones 5 and 6.

WS is indeed very successful here in zone 3. Like anything else, though, there are successes and failures. On the whole, i would give it two thumbs up. I often start when there's a mild day during the Christmas holidays, but that depends on the type of seeds you want to sow. Some need a longer period of stratification (exposure to cold), so you do them earlier. I continue off and on throughout the winter, doing it when better conditions (i.e. not -30!) coincide with weekends. I do a lot during March Break and usually do the annuals around Easter. After germination, i only protect the annuals if there's a heavy frost threatening - i then move them all into my cold frame and cover it with a blanket.

If i look throughout my gardens, many, many, many plants are there as a result of winter sowing. :)

There are several of us in Calgary who do WS successfully.
It is one of those things which you have to try, and then see what works and what doesn't. It, like all gardening, does depend on the weather. What works one year may not the next etc.

The weather is a big variable for sure. Always make sure you have drainage holes in your containers and keep them somewhere out of the wind and away from where pets and kids might be walking and playing. When it's dry, i put my containers into trays so they can soak up water, but of course that's sure to bring on the rains, so out they come and i'm putting them under my big outside table so that they don't drown! LOL

Well, it seems it's worth a bit of research, and for the sake of a bit of dirt and some milk jugs, what the heck =:)

Can any of you suggest what might be the easiest and most likely to succeed?

Peas, beans, marigolds ??

I'd do marigolds before i'd do beans or peas. They work fine direct-sown into the garden. Marigolds work well, as do calendula, alyssum, cosmos, zinnia, ice plants, amaranth. For perennials, there's columbines, lupines, dianthus, heliopsis, hesperis matronalis (have you been studying your Latin yet? LOL), polemonium, lychnis, penstemon...

Hesperis matronalis (Dame's Rocket)

Lupines:

Ice plants:

Malva:

Heliopsis:

Well, this isn't getting the tree decorated....

But there you go - if you want to try winter sowing this year, i'm sure we'll be happy to answer all your questions!

Holy cow Marcia. Did you winter sow all of those in the pictures? Are those blooms from the first year ?? Hmmm. About the Latin......

ljpother - I think I'd be concerned with the temperature fluctuations here, too. xaroline would have those in Calgary, that's for sure.

Is it possible to winter sow in an unheated garage? Once the weather warmed a bit, there wouldn't be such a change in temperature in the garage.

I'll have to do some reading and figure out which questions to ask.

Eek! Marcia - you said you start some during the Christmas holidays. Which ones? I better save some milk jugs soon!

I have 600 litres of water in my greenhouse which generally keeps the overnight temperature from going below freezing. The days that cause trouble are overcast and cold. I don't gain enough heat to hold at 0C. Above freezing I get an extra 2-3C over outside. Without the overnight freeze, my germination is earlier than outside. Most of the plants that germinate survive. However, I want to start my tomatoes earlier this year and will turn on an oil heater about 3C. This should give me an extra month.

In jugs I would stick to hardy perennials and annuals. Cole crops should do well. If you have the seeds, take a chance on tomatoes and other tenders. In theory, the tender plants won't sprout until it's warm enough. I have more faith in that happening in North Carolina. :)

No, i don't think they bloomed the first year - some of them do, like foxgloves and dianthus, and probably the lupines, but i can't remember for sure. The ice plants are annuals, so of course they bloom right away. I just wanted to show you some of the plants i have now that were winter sown. I could go on! LOL

I wouldn't winter sow in your garage. Leave them outside. Seeds that fall on the ground from plants in the garden don't go into a garage or anywhere else, and many of them germinate easily.

Checking my notes, this is what i've sown in late December or early January:
aquilegia
Allium (no luck with that, though)
Lupines
Meconopsis grandis (no luck there either)
Adlumina fungosa (i don't remember the common name for this but it did germinate and was planted, but died after a couple of years)
Baptisia
malva
Gentiana andrewsii
Geranium (hardy not annual)
Dianthus
Erygium
Echinops
Achillea
Hollyhocks
Coreopsis
Delphinium
Penstemon
Clematis tangutica
Echinacea purpurea

I've just included the ones i had luck with. I can't remember when the perennials above were sown - i started this about 5 or 6 years ago.

Thanks everyone!

I'll post any remaining questions on the Canadian Winter Sowing Forum.

If you're looking for information on types of containers to use, type of soil, etc., look at the FAQ section on the Winter Sowing Forum, the main one, not the Canadian one. That's where I got most of my information.

Oops! I guess I fibbed. I said I'd ask the rest of my questions on the WS forum, but.........

I've ordered some seeds and I'm saving my milk jugs and I'm chomping at the bit and anxious to start.

I haven't been able to determine yet where I should plunk my experiments. Should they be in a place where the snow will melt first in the spring, or should they be in the biggest snowbank I can find? We have lots, so that wouldn't be a problem. I'm just wondering about when they should be exposed to the elements.

I had good luck in northern MN with winter sowing. I would put my jugs/flats in an area that would NOT get the first of the spring sun. That way they were a little bit slower to come up, but had more protection having sprouted a bit later when they did. The biggest issue I had was protecting the seedling pots from the wind!

I planted out directly a bunch of wildflower seeds from several sources last spring. Hardly any sprouted. Might they still come up this coming spring or is that wishful thinking. Northwoodswis4

It is hard to say with the wildflower mixes, they are so variable as to the mixture. Often they will have annuals and perennials mixed along with a certain percent of grass seeds. Getting a wild flower garden is actually a lot more work then most people understand (or are marketed to!) but there are a lot of good information sites for establishing them if you do a google search. I used to just toss a bunch in and around my garden beds on occasion but don't think it was really very productive.