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Damage to my tomatoes from propane heater, help?

Peru, VT(Zone 4a)

I have a 6 x 8 HFGH with a Buddy propane heater in it. People on different forums I have read have said that they had one of these in their greenhouse without plant damage. But my plants are having a problem, most especially my tomatoes.

The heater is functioning well, hooked ups to the tank are tight and my greenhouse can't be airtight. I'm not sure how to fix this. Can anyone help?

Dublin, CA(Zone 9a)

Can you post a picture of the plants you're having trouble with, or at least describe the symptoms? It could be your GH is more airtight than you think it is and the heater is causing the problems, but it's also possible that it's something else--there are plenty of other things that can go wrong in a greenhouse. The problems caused by heaters that aren't vented outside the GH have to do with the byproducts of combustion (carbon monoxide, etc) so having the hookups to the tank tight won't help with that.

If the problem is the heater, here's some info you may find helpful:

Durhamville, NY(Zone 5b)

This site gives a good overview of the problems of an unvented heater.

Peru, VT(Zone 4a)

I just wanted to update this. I know there can be problems with unvented heaters. But finding an appropriately sized vented heater with a reasonable price for a 6x8 greenhouse is hard, too. And electric is too costly.

I think my greenhouse was tighter than I thought it was with the pool cover I have on it, and the insulation I have added. So what I have done so far is add a 3" pipe to bring in fresh air behind the heater. Then I added a fan that's on all night, a little clip-on desk fan (I have a greenhouse fan but it's on a temperature control so it doesn't run all night).

My plants are looking a lot better but I still don't think I'm totally out of the woods. I have started some potato seeds (not seed potatoes, potato seeds) and those seedlings look a little off.

My Buddy heater has only two options, High and Low, and I am heating the greenhouse more than I would like to. It can get up to 70 in there at night when I only need it at 50, which is exposing my plants to more combustion products than I need to. They just came out with an unvented icehouse heater that has more settings that roughly correlate to temperature.

Durhamville, NY(Zone 5b)

I think I'd also ad a small vent near the roof of the greenhouse since the little heater is heating it more than you need. It should help carry out pollutants and allow more air to come in the 3" pipe.

Lewisville, MN(Zone 4a)

We have a 24 x 60 greenhouse. Ran a propane heater only a few hours one cold morning. Killed some plants, slowed up many others! Threw the dam*** thing out. Would have been better off taking a chance with the freezing temps.
We since have our fuel oil furnace going with no problems.
Gas has a history of blowing buildings apart, killing people from fumes. Best left in the ground!

Other than our greenhouse of place is all electric heated, house, wood shop & chicken barn.

Seems electric has no fumes!

Whitesburg, TN(Zone 6b)

"fumes" from propane consist mostly (99%) of CO2. CO2 helps a LOT! The fumes are not your problem. You are probably lacking humidity. Tomatoes like heat, but not dry heat. You need humidity for tomatoes. Put a pot full of water in your greenhouse in such a way as to keep it hot. Keep it full of water and the humidity will be high. Check it regularly, it will diminish quickly. You need to fill it often. Tomatoes like 100% humidity and 100 degrees Fahrenheit, if possible. It needs to be close to raining inside for them to thrive. When you wake up in the morning, there needs to be drops of dew running down the inside of the greenhouse. Take it from a South Carolina Gardener, the more humidity...the better!

Lewisville, MN(Zone 4a)


Durhamville, NY(Zone 5b)

Actually burning propane will be approximately 42% CO2 and 48% water by volume. The problem comes from the minute quantities of other things that are produced. One of these is ethylene gas which tomatoes are very sensitive to. Look at this link.

The damage starts at .01 ppm. How much gas does this translate out to be in a 6' x 8' x I assume average 7' tall greenhouse?. That calculates out to 580,000 cubic inches. .01 part per million is .0058 cubic inches of ethylene gas in that greenhouse. That is the amount of gas that would fit in a block that is 1/6 of an inch on each side.

Whitesburg, TN(Zone 6b)

"Whatever!" ? Very intelligent reply. Thank you for your contribution.

Yes, propane makes some water too, but of the gases that it produces, 99% is CO2. Ethylene would be a problem, true. Ethylene is the gas that commercial producers use to artificially turn tomatoes red after they are picked green so they can be shipped without damage. That is why some grocery store and restaurant tomatoes are red, but crunchy. Also, ethylene forces pineapples and bananas to ripen. Of course, this is the fruit, not the plant that they are exposing.

Ethylene is soluble in water, so you could vent your fumes through a water trap/bubbler device to reduce the amount leaked into the air.

Have you thought of a passive solar heater? 55 Gallon black barrel full of water, for instance?

Lewisville, MN(Zone 4a)

People on this site like to think there are multiple answers to things. Propane gas fumes will fry greenhouse plants, plain & simple. Ever here of people overcome in their own home ? Same thing!

Liberty Hill, TX(Zone 8a)

I've never seen tomatoes produce a thing if humidity or temps are 100 or 100%. I do know that those conditions denature the pollen. Ethylene is naturally produced by many fruits. That's why wrapping tomatoes in newspaper and putting them in a dark place will promote ripening. The gas is already there it dissent need to be added, but it can be.

Mike, I don't know you, or your background, but if I needed help growing just about anything, especially tomatoes or peppers, from seed to production, Bernie would be one of the first people I'd ask and he's never failed to answer.

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