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what's the lowest temp that most veggies/plants can handle

Posted by rjinga middle ga, zone 8 (My Page) on
Sun, Oct 7, 07 at 21:43

When my GH is assembled (hopefully by the end of this month) I'll be mostly storing my patio plants (ferns, geraniums, peace lillies, etc and some tropical trees and vines. In addition I have recently germinated and will probably have some basil and cilantro and parsley seedlings to grow out there.

Since we do have mild winters with only minimal number of freezing days...I can easily run an extension cord out as needed with some kind of heater.

If it's kept closed up...and let's say it is in the 40's or 50's outside....will it be warmer inside just as a rule, from it's own insulation? what can I expect with this?

AND, what is the lowest temp most of these plants I mentioned can tollerate on a daily basis with (without heaters) and without kicking the bucket?

Just gearing up and getting prepared....

Follow-Up Postings:

RE: what's the lowest temp that most veggies/plants can handle

  • Posted by f150dude 7a/b South Jersey(Wi (My Page) on
    Mon, Oct 8, 07 at 15:36

As long as the GH gets the sun exposure during the day, if it's in the 40's or 50's outside (during the day), it will be much warmer, depending on the size of the greenhouse. If it's small, it will rise fast, if it's bigger it will take longer to heat (w/sun) but it will still be warm. At night, if you are not heating the greenhouse, eventually all the warm air will escape. SO if the temperature is 50 overnight outside, then you should be fine (check the veggie seed packet for low temperature allowance).

Also, if it's warm outside, make sure the seeds and plants get much water. Most of it evaporates during the day.

In my greenhouse, i have spider plants, geraniums, wandering jews, and a tropical palm with large oval leaves (kind of resembles Banana Tree). The lowest i kept my greenhouse was about 42F. As long as it doesn't get below freezing in the greenhouse, they did pretty well. I had parsely and Basil in the greenhouse last winter and they survived until summer, i didn't water them once i brought everything outside.

Hope all this helps, let me know if you any other questions!!


RE: what's the lowest temp that most veggies/plants can handle

You have alot of loaded questions in this post.

First, let me just restate what is often not well related about "UNHEATED" greenhouses. They will all usually have an inside air temperature equal or only slightly higher than the outside temperature by night's end. Even those who use various heat sinks have found that by the next morning their reserve heat is gone. This isn't to state that all the insulations and heat conservation methods aren't great. You will need much less supplement heat (if any, depending on crop) than you would otherwise.

When the sun comes up everything is different. The temperatures inside will likely get too hot even in the middle of winter on a very sunny day. Some way of ventilating that heat without introducing a cold draft onto your tender plants is important.

I've grown cilantro in PA overwinter without any heat. I think it is only slowed in growth by frosts. Parsley would probably be similar once you get it started. We have cut parsley in December although regrowth is much slower then. Basil is a different crop. It won't do near as well if you have cool nights. Leaves on established plants may discolor if temperatures drop near 40F. It is a sensative annual.

In my opinion you could grow the cilantro, parsley and a host of other greens and eliminate the expensive heat. Since parsley is a biennial try to isolate it so it won't interfere with other planting practices. I would wait for warmer weather to grow basil.

RE: what's the lowest temp that = rjinga

Here in TN my GH isn't much warmer at night than the outside air by 1 or 2 AM. I grow both cold tolerant and cold sensitive plants so kept the GH at 60F last winter. Cooling it on sunny days was more of a problem than heating it at night. I would open one roof vent and leave the door open an few inches. But then someone would have to be home at sundown to close it up again. :(

The Rion has auto-vents so heat may not be such a winter problem with it - plus it has more fans.

RE: what's the lowest temp that most veggies/plants can handle

Hi rjinga.Good luck on your new adventure!!I live in North Georgia-and I have a more difficult time keeping the greenhouse cool,than heating it.Mine has a thermostat controled vent fan.In january,when the sun is shining,no matter how cold it is outside,the vent fan comes on about every 10 minutes all day long,to keep the greenhouse down to 85F.Without the electric vent,it would probably get 130F.I use a propane heater(we do lose power because of ice storms here about every other year)-but in south Georgia,You should do fine with an electric heater.I keep my heat set on 50F.Like everyone has said,a few hours after the sun goes down,the inside of the greenhouse is nearly the same temp as outside!!!

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