January 17, 2024

Freezing Temps & How the Greenhouse Is Doing

While nowhere near record breaking, this morning's low put the greenhouse to the test. 

  • outside low: 12°F (-11°C)
  • inside the goat barn: 22°F (-5.5°C)
  • inside the greenhouse: 25°F (-4°C)

The result was freeze damage to my warm weather plants: cherry tomato, green peppers, and potatoes. None of this is a surprise, of course. What has been a surprise is that previously, everything survived an outdoor low of 20°F (-6.6°C).

At this point, the only heat the greenhouse gets is residual from the house. It has three glass window walls with the fourth wall being the exterior wall of my sewing room. I don't know how much this actually helps, but I suspect it's better than if the greenhouse was freestanding with four glass walls. 

So there's my baseline. Hopefully, we'll be able to increase the survival odds with some other ideas. 


Michelle said...

Do you have an electrical outlet in the greenhouse? Would it work to put heating pads (the ones they make for seed-starting trays) under your warm weather plants, and then drape light fabric over them to protect the uppers? That would be SO much cheaper than trying to heat the space.

Nina said...

Several people I know just layer fresh manure down, under their trays. It can give off enough heat to keep greenhouses warm. A friend also uses the manure layer in her cold frame for starting plants and they do wonderfully well in that. Another friend just has 45 gallon drums of water, but she's also put a brick floor in to set them on, so the floor as well as the drums of water work as heat sinks, which keep her greenhouse warm as well. Having an idea of temperatures will really help you find whatever way works best for you.

I had lots of water bins for heat sinks one year. It kept both the temperature warm and the humidity nice. The drawback was that we had a garter snake which thought so too, and it took over the plant beds until he shed his skin. That was an interesting few weeks....

Toirdhealbheach Beucail said...

Thanks for the update, Leigh. Is that the actual outside temperature or does it include wind chill as well? Here the wind chill has been dropping the temperature another 10-15 degrees outside.

Sue in Oregon said...

Would be an interesting and fairly inexpensive experiment to get some glass filled candles from the Dollar Store and light them on cold nights. When I was growing up in Texas they used to put smudge pots in the orchards to protect fruit trees. Always amazed me that something so small could be so good against frost.

Leigh said...

Michelle, no electrical outlets. I've been collecting ideas for non-electric ways. Then too, I'm not really planning on trying to grow summer crops in winter. But the tomato vine was a volunteer, and so a good experiment.

Nina, we have all of those ideas on our list of things to try. Not sure if we'll get to them all this winter, but we're working in that direction!

TB, 12 was the air temperature. Not sure about wind chill. Fortunately, there wasn't much wind when we went out to do chores this morning!

Sue, that's very true about the smudge pots. I've seen some interesting ideas using candles and inverted terra cotta pots. That's another idea to try.

Ed said...

I can easily gauge the freezing/not freezing aspect of my greenhouse from my living room chair. It the snow on the roof stays put, it is below freezing. If not, it is quickly coming off.

As you know, we did the large water container as a way to even out summer temperatures. If I had a greenhouse attached to the side of my house, I think the easiest and probably most economical way to provide enough heat to keep it from freezing on the coldest days of winter would be to crack the door between the house and greenhouse open for the coldest hours. I don't think you have your door installed yet but perhaps next winter that can become an option.

Normally, it would probably never be an issue for you but thus far, January has been one for the record books and another cold blast is heading our way this weekend.

daisy g said...

Your readers have such great ideas!
We shared the 12 degree low here in the Piedmont of NC. That is dang cold!

Leigh said...

Daisy, yes lots of good ideas. I've been collecting ideas on pinerest as well. I'm considering this my baseline year, with things only getting better!

Nancy In Boise said...

Maybe free standing kero heaters? Sorry for your warm weather babies!

Leigh said...

Nancy, I honestly didn't expect them to make it, so no actual sense of defeat there. A kerosene heater is an option, but I'd like to try the simplest ideas first. I think our next one will be thermal mass from rainwater collection. Dan's not terribly hopeful on that one, but I figure every little bit helps!

The other consideration is that I'm not really planning on using the greenhouse to grow warm weather veggies in winter. We're just testing the limits for now.

Fundy Blue said...

Hi, Leigh! It's been interesting to hear some of the ideas people have been suggesting. In Colorado when there is a freeze warning, people cover their at risk plants. I have no idea if that would work in a greenhouse. Good luck!