Unheated Greenhouses

[tortoise]

The real test is overcast days with freezing temperatures preventing any daytime heat gains.

We had one overcast day with no heat gain. It was windy so I left blankets over the domes all day. I was surprised it maintained temp overnight. But that will be different when the ground freezes.

 

[Britesea]

Yes, most plants do not actually Grow during the darkest months- they go into a kind of suspended state, but you can still harvest them. Also, I seem to recall that Elliot Coleman said that if the plants (greens) actually appear frozen, don't touch them. Often when they thaw, the plant is still ok, and you can even harvest those leaves to eat- just NOT while they are frozen.

 

[Mini Horses]

If you can't get a greenhouse up, you can do minis with the basement access covers they sell at big box stores. Even good as covers for a raised bed next to house foundation. I have a couple shower slider doors that were free and I've used to cover both plant and brooder boxes! They're framed and have a handle....could be used as part of a cheapie greenhouse build, as with old windows.

 

[Britesea]

In your zone, and indeed in mine as well (Zone 6), plants don't actually grow during the winter months- probably because there simply isn't enough sunlight. But if you start them early enough to get some good size on them before the short days, they will go into a sort of stasis- you can harvest them, but they won't put on much growth. Your perennials might do just fine in the greenhouse (they won't need a lot of water, but you still need to check that at least occasionally- I lost my rosemary because I forgot to check), Lettuce may do ok. The best greens would be the really hardy ones like endive and chicory, and especially mache, which is the most cold hardy green I know of. In fact, it won't even germinate in warm weather, lol. I didn't start things early enough this year with everything else going on, but things like chard and kale and such would probably do well too.

 

[tortoise]

All a greenhouse does is increase the temps when the sun is up.

It has close to zero insulation,

I dont think the wide day-night temp fluctuation helps plants much. Mine is on patio pavers that retain some heat so it does better in late fall than early spring.

 

[Britesea]

All a greenhouse does is increase the temps when the sun is up.

It has close to zero insulation, but it does help with protecting plants from wind.

If you want a greenhouse to hold heat then it needs to be partly sunk into the earth, proper insulated roof and proper double pane windows.

I have seen plans where the entire greenhouse is sunk below frost level, and I have seen other plans where you have something like infloor heating in the growing beds.

There are some creative things put there.

But for zone 4, in the winter time grow stuff indoors.

I think that the greenhouse does slow down the drop in temps at night, even if it doesn't completely prevent it. Typically, when I go into my greenhouse first thing at sunrise, it's about 10 degrees warmer than outside; I don't think it rose that much from the 10-15 minutes the sun was over the horizon.

I really miss my max/min thermometer from California. Somehow, it didn't make it in the moving process. It was an old fashioned one- no batteries or liquids- I believe it used the principle that some metals contract at certain temps more than others, or something like that. Anyway, I've never found one as good, and I really miss it.

 

[R2elk]

I dont think the wide day-night temp fluctuation helps plants much. Mine is on patio pavers that retain some heat so it does better in late fall than early spring.

Mine is on my deck with a window to a bedroom in the house. I leave the window open during the winter. I put insulation under the greenhouse floor. I do not keep plants in it from December through February. In March I have an electric heater rigged up with a thermostat to prevent freezing temperatures.

 

[tortoise]

Mine is on my deck with a window to a bedroom in the house. I leave the window open during the winter. I put insulation under the greenhouse floor. I do not keep plants in it from December through February. In March I have an electric heater rigged up with a thermostat to prevent freezing temperatures.

I want my greenhouse on the deck right against my patio door. DH says no because the gaps between the deck boards. (Isn't that why God gave us green treated plywood?!)

 

[frustratedearthmother]

That is way cool! You did a great job.

 

[tortoise]

Gorgeous! I am envious!