adamcozzie - I was told by a wise old man that kerosene was safer than just about every other source of heat. It is the liquid itself that catches fire and not the fumes so it rarely explodes like propane or gasoline. The biggest problem would be if the heater got knocked over while it is lit - which could happen if a wind storm blew over your greenhouse in the winter. Even then, only the puddle of kerosene would be on fire and it will burn itself out. It costs about the same as premium gasoline if you can find a gas station that sells it. Buying it from a home improvement store, you'll pay about three times the price per gallon. Even a little kerosene heater will put off a lot of heat. The only problem with the tiny heaters is that their fuel tank isn't large enough to hold enough fuel to burn all night long so you will have to get up and reload it during the night (no fun at all). The same warnings about burning a kerosene heater all night or while unattended are pretty much the same across the board with all heat sources. It isn't safe to burn anything.

Two things: 1) I think i prefer to go with something like in ebay just for simplicity and something like this would only take minutes to set up. Yes i build a bigger green house (which i don't need) or maybe build it cheaper but $150 is cheap enough for me 2) could you be a little bit more specific on Heating/ventilation needs? If needed i guess i could run an extension cord from the house out to the greenhouse with a space heater to keep the temperature at least in the 40s if the temperature gets really cold. I could also daily open up the greenhouse for a little bit just to allow for some ventilation. These are seedlings that im trying to grow and i don't expect they will run out of C02 in a day. I'm assume the greenhouse will just get warm from the suns energy but of course since i never owned one i don't know how much. I need to know if im over my head here because i don't want to blow $150. ncage

You could build the grow room in the garage for winter and get a collapsible greenhouse for the early spring, summer, fall.

Thought I'd report back on germinating beans with a nitrate solution. (Only a third [8/24] of my beans planted in ground earlier in May had germinated). In the cell pack with Miracle Grow I planted 72 beans. Thirty one germinated, so 43%. The cells were too small, so that a couple of beans got their roots growing over the stem, so that they could not get up out of the soil. Pretty weird to see a bean with true leaves trapped in the pro-mix, coiled twice,yet not able to escape the roots. Those roots were partly above the soil. Also, some beans came up with oddly thin stems. (That was the case in the garden as well.) Quite a few had trouble completely splitting their seed coats even after their were well above the soil, so I gave them a little help with that. Tonight I planted out as many as I could. Will be interesting to see how many survive transplant. I left the weaklings in the cell packs to see if they will develop any more. I still need to plant out a lot more but I'm going to move on to my seed purchased for 2018. Got to get them in pronto.