Unheated Greenhouses

[tortoise]

I have been unsuccessful in using an unheated greenhouse in zone 4. Can anyone help?

My greenhouse is 8×10 feet, aluminum frame, plastic panels. It has been useless, TBH.

 

[R2elk]

I insulated under the greenhouse and covered that with cheap flooring plywood. For the floor of the greenhouse, I put the same stuff over the deck 2"x4"s covering the gaps. I put a wood grain linoleum over top of the flooring plywood. No gaps to be seen now.

 

[R2elk]

Currently in the greenhouse.

 

[tortoise]

My sacrificial seed trays 😅 They are planted with romaine and chard seed that had spilled in my seed box. I put the thermometer inside of one of the trays.

Background is DS6's patio pot of cherry tomato and a red romaine that bolted and is blooming.

 

[Mini Horses]

Well mine would certainly be an enclosed sunroom porch where I could start plants, not a true greenhouse! That's ok....would suit me well. There's a solid roof over it, not going away. I actually would prefer windows from rails up, solid clear wall on lower area...I'd have a warmer place to sit and to start plants or chicks. 😁

 

[Alaskan]

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.

 

[tortoise]

Day 5

Same seeds, also Day 5, grown indoors under artificial light

 

[tortoise]

I forgot to cover greenhouse domes until hours after dark - 9:30 p.m. greenhouse temp was 41.

This morning its 43. Its gaining a couple degrees from the ground/patio block. Good to know. 👍

 

[Britesea]

an unheated greenhouse is basically a cold frame you can walk in. If you need to keep things a little warmer, there are a few things you can do.
1: try putting a second layer of plastic or frost cloth over the plants INSIDE the greenhouse. According to Elliot Coleman, every layer of frost protection increases your zone by 1.
2. if you have room, place barrels of water in the greenhouse, near the most susceptible plants (metal works best, but even plastic will help) As the temperature drops and the water begins to freeze, it releases energy in the form of HEAT. This is why watering your plants before a frost can sometimes help the plants in the field.
3. if you have access to fresh manure- put a bunch of it in the greenhouse. As it rots, it will release heat. This was the origin of the "Hot Box" as opposed to the Cold Frame.

Last but not least, choose to grow cold hardy plants, and give up on the idea of fresh tomatoes at Christmas, lol, unless you can grow them inside your heated house.

 

[tortoise]

Overcast day, 64 degrees F outside.

Inside the dome, its 81 degrees.

I will have to watch carefully on sunny days. Seedlings cant handle temps over 90 degrees.