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Texas Gardening

Greenhouse temps last night

14 years ago

Mine got down to about 28 and some stuff froze, I'm just using a little 1500 watt heater and some really old christmas lights for heat, keeps it about 12 degrees above outside temp. What to do to keep it warmer? Using a Harbour house 12x 10.

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Comments (7)

seamommy
14 years ago
You can buy a little portable heater at Walmart that has a thermostat on it. I use one in the loft room over my garage. The room is 18' x 24' and this little heater keeps it comfortably warm up there all winter. I think I paid about $30 for it. Cheryl
kentuck_8b
14 years ago
I've got two greenhouses. One is 10' X 14' and the other is 16' X 40'. I just went out and checked the heaters.

In the smaller one, I just use a 1500 electric heater and it does about the same as yours, keeps it about 12 to 15 degrees above outside temps. It was 15F this morning, but everything did OK.

In the larger greenhouse, I use a kerosene heater, but added an electric heater this year as a backup and to use together on nights when temps get really low. It was 42F this morning in the big greenhouse.

In years past, I would fill large tubs(20-gallon black plastic) with water and set them along the outer edges(on the inside) of the greenhouse. During the day, the heat would warm the water and radiate it back into the greenhouse after dark, helping heat the greenhouse. I didn't have room this year for that, but wish I did, it really helps.

Kt
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Oh you'll be surprised how cold things can get and still survive. I've seen 26 degrees in my home made simple greenhouse and my super tropicals came through without a scratch and some of my supposed-to-be hardy plants died. It all depends on what kind of cold it is - is it humid? is the air moving around inside the greenhouse? how long did it stay cold? Portable electric heaters usually top out at 1500 watts and all pretty much give you the same amount of heat. You can't run anything stronger on a normal power cord. I use one under a tent of thin plastic sheeting set up inside the greenhouse. Sort of a greenhouse inside the greenhouse. You'd be surprised how warm it keeps things (you have to keep it small, I use it mainly for orchids). I use a regular kerosene heater for back up when things get really cold (I'm in zone 7b, Raleigh NC). A standard room heater cost around $135 at any hardware store. The killer is that you HAVE to buy the super expensive fuel - 5 gallons for $45. It will be clear and usually low odor. The cheaper red-dyed stuff will clog your wick in a couple of months and wicks are impossibly hard to change. Though stinky and messy they give off a huge amount of heat. Keep in mind that some plants are very sensitive to Ethylene gas which is odorless and given off my burning kerosene. My current greenhouse is large and I can just move anyone having a problem 10 feet away and the problem goes away. I now have an old massive wood burning stove as my primary heat source and love it. Wood is next to free for me and the blower unit on the stove moves a lot of air. I can normally get a 20 degree gain with just the wood fire and an extra 10-15 if I run the kero heater at the same time. Last night was 24 around here and the greenhouse stayed above 50. The downside (besides being very messy) is that the fire has to be managed all night long. Sometimes I can damper things down and get 3 hours of sleep between fire tending but other times everything burns up in an hour - it all depends on the wood and the humidity. You always want to have a small fan blowing the air around no matter how small your greenhouse is. I find the cheap plastic floor fans with the largest blades move the most air. A lot of "tropical" plants can handle a light frost without damage, even orchids and bromeliads. They just can't handle it every night. Once or twice is about all.
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STEVE--you had me ROFL. "Mow and blow boys"--PERFECT! That must be why they've been removing trees and chopping huge limbs off trees all over the place in the past 2 weeks. It will easier for the ignorant little rodents to just push a lawnmower straight, over grass, than G-d forbid have to veer to go around a tree. The other week, one of them was using a leaf blower to blow huge clouds of dust and particulate matter straight up into the air. What a great way to spread hanta virus from mouse droppings and create a respiratory hazard for asthma patients in the complex. Wish they'd all just go back to wherever they came from. The hostas and squirrels have a higher I.Q. than they do. Basic concepts such as "Don't trample my plants/fences/plant markers" seem to elude them. Their absolute ignorance about plants is glaringly obvious. In this, they remind me of The Cretin, AKA the co-op manager. Dang, this is a regular phyto-Peyton Place here! Someone could have a long-running TV series: "The Day the Hosta Died" "A Tree Doesn't Grow in Flushing" "Did You Seed What I Seed?" "Gunfight in the not-OK Laundry Room" "Dangerous Adirondack Fencing Liaisons" "Heuchie-Coochie Coo" (A Baby Heuchie Grows Up) "I Spirea" "With Clean Hands and a Pure Heart" "Stomp the Yard (if yer an igno 'landscape worker')" "Breaking Away (the leaves on my plants)" "For Whom the Coral Bells Toll" "The Good Earth" (schlepped home from Home Depot) "A Hard Day's Night" (I work through the night to add the 18" extension to my garden so the maintenance guys won't rat me out) "I Remember Trauma" "Spray Misty for Me" Have I forgotten any episodes? Help me out here!
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suz52
14 years ago
I freak if mine gets much lower than 38-40.....I have used several methods over the years. I use a little space heater and a propane heater. I'd use 2 electric, but I'd blow a fuse...LOL
cynthianovak
14 years ago
We have an 8 x 16 with twin wall poly siding. The roof is tin. 3 nights ours fell to 29. Some leaves are crispie on larger plants on the north side...where the thermometer sensor lives.

We use 2 of those electric heaters that look like small radiators. They circulate oil within and are efficient and no coild exposed to worry about.

Sorry that some plants froze, but most will survive from their roots.

We used to us propane, but it always made me nervous. Lighting the heater etc etc. We do use two different outlets and heavy duty extension cords. 1 or both heaters ran for nearly 3 days. Yikes!
jerrytx
14 years ago
Texazgal; I used 2 rolls of duct-tape around the areas likely to be "leaky", as well as my 1500wt. heater, outside temp was ~19F, but greenhouse min temp. was~39F. my greenhouse is 8 x 12 twinwall poly. I had used a similiar trick that Kentuck uses, I bought 4 used 40gal. drums filled with water and placed around the outer walls of the greenhouse, and it did help. ( unfortunately, as small as my greenhouse is, that don't leave a lot of flexibility for organizing things) Another trick you may try, is to pile any leaves, or pine straw against the outside lower part of the greenhouse. This would help but only by about 2-3 degrees. I was fortunate, this time, have tomato and pepper plants started, but I have them on a heat mat, and that could have helped keep the temp. up some. Hope your plants come back o.k.
Jerry
spishack01
14 years ago
I haven't checked mine yet, too scared!
hitexplanter
14 years ago
The greenhouse forum (at least in previous years) has had lots of useful tips and ideas of how home grown greenhousers survive in worse weather than ours... worth lurking on even if you don't ask any questions I would expect you to learn several good conceptual ideas that you can adapt to your situation.
Happy Growing David

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