In my book growing in a greenhouse isn't wintersowing as we speak of it either. But some folks here do have greenhouses and maybe they'll be able to offer help. I'm clueless about greenhouses.

Karen

Karen and I must have the same book, because I don't really think of growing in a greenhouse as winter sowing as we speak of it either. I suspect you'll get your best information if you post your question in Conversations. There's a lot a activity there this year, and as Karen mentioned, several people have greenhouses.

Wishing you a successful gardening season,
Seedmama

While greenhouse will have higher humidity I would think seed tray still need to be ecnlosed for germination purposes. It also will depends on where your greenhouse is located, how much sun it gets, how much temps are going to raise and how much venting you are going to do. Most seeds germinate well in range 65-75-80 temps of soil. Anything above that liable to stop germination. If you have your greenhouse in direct sun all day and temps are going to be 70 to begin with it means that at some point temps in your greenhouse will be over 100. In such case I would either shade tray or uncover it.

I don't know about it not being considered winter sowing. How is an unheated greenhouse different from a cold frame?

I w/sow in flats and put them in a shade house that has the shelves covered in plastic. I keep the plastic domes on the trays. I don't consider it an unheated green house because the table is 1/4" hardware cloth so exposed to plenty of cold weather. I will however take the domes off this week as our temps are going to be consistently about freezing at night and upper 60's during the day. They get a misting almost everyday so the surface doesn't dry out ......

Lynne

I would cover them only until germination begins. After that, I would leave them uncovered and maybe even sit them outside if it's above freezing especially the colder veggies. Any annuals I would leave in the greenhouse, but use a fan.

I use a glorified cold frame for some things like my annuals. The petunias have been done this way. Whenever the temperature is supposed to reach 60 or higher, I open it up each morning, early. And close it after dark, but before a frost can develop.

As I mentioned in another thread, an unheated greenhouse is essentially a walk-in container. I don't think the heat management is much different than the small containers. They all need venting on hot days. Although, the heat gain from glass is likely greater than from plastic. 23C for the high today or yesterday, -5-10C outside.

I watered the flat and planted Scarlet Runners, morning glory, and zucchini in starter kits. Also, I put a plastic bag over the flat. It was dry.