In winter sowing we want the containers to be in the elements bec. this is what produces hardy plants.

but seems to me your idea should work, sorta being between growing indoors, and winter sowing.

can't say I have tried it, interested to see if anyone has

I think that's okay. Just be sure to keep the containers moist (not sopping wet) and if you can I would put the greenhouse in part sun so it doesn't get too warm. The elements are good because Nature provides the light, moisture and temperatures required for the seed to germinate and it's so easy. Nature does the work.

But there are variations. Last year I sowed some Magnolia grandiflora seeds. In general southern Magnolia is not a very hardy species, although these seeds came from a tree in the Arnold Arboretum in Boston zone 6b. So for insurance I sowed 4 containers - put 2 in the garage (so the seeds wouldn't freeze) and 2 out in the elements. The garage is cold like a refrigerator all winter and I kept the containers moist, watered about 1x per month, so they got cold stratification.

Lo and behold, I got 3 sprouts in the containers in the garage, but none in the containers outside. I think the seeds froze.

I would give the green house a try!

Barb,
Just remember that your unheated greenhouse can be really warm inside. So keep an eye on the temperature as well as the moisture.

Best of luck!!

Barb,

I have been greenhouse growing for a couple of years now. I do it in cups like winter sowing but they go in the greenhouse instead of under plastic. They get the cold period they require and once or twice during the spring thaws, I shovel snow onto the cups for water.

I do the same with hardy/half hardy annuals, no heat just moist cups out in the winter. I add in the tenders around April 1st and I heat this one to around 65 degrees at night.

As soon as it warms up a bit, I just take the hose to them daily for water.

I have had great results, try it, it will work great. It's a lot less work than all those milk jugs too.

Lisa