I live in a cold climate "zone 6a", and i would like to give a head start to my plants and extend my growing season, so I plan on building a greenhouse early spring My last frost date is May 3. Would it be safe for me to put plants in the greenhouse in April when the nights are going below freezing?
Well I just hope this link helps @adam.ca in the meantime, until members help you who know what they're on about more than me, as I've never owned one. https://www.thompson-morgan.com/heating-greenhouses-over-winter
Adam, I don't know either. I have a cheap plastic one that I use to harden off seedlings, and then nurture them until they are ready to go in the ground. Mine does extend the season somewhat. @carolyn will be better suited to answer this question. She may be zone 6. Or 5.
Probably not without some sort of heat at night ! But one of the little electric heaters work on a thermostat and can be set to turn off and on to keep the temps above freezing ! They are inexpensive ! You would just have to remember to turn off and on ! Unless its really cold you likely would not need in daytime !
In march ill build it, and stick a thermostat in there and see if holds any heat. I'm going to line the back wall of the greenhouse with a bunch of 2L bottles, painted black, filled with water, for "thermal mass" and also I'm going to try to make a "hot compost pile" at the bottom of the greenhouse. we'll see if that works at all.
It depends on what you are growing. Tender things such as to atoes and peppers, eggplant, melons, cukes etc... Not safe unless you cover them if there is a freeze or frost warning. Lettuce Cole crops etc would tolerate cold weather. We grow in a high tunnel which has no heat and we cover the plants with floating row cover when it is getting below 45f. Tomatoes are forming a bud much sooner than you ever see the tiny bud.. When the plant gets cold it shows later as deformed, catfaced,zippers or other imperfections as the fruit starts to form.
@carolyn I'm learning a lot, and coming up with a strategy, I'll move all the plants that have some cold tolerance into the greenhouse early hoping the greenhouse will offer SOME protection, and that the cold tolerant plants will be fine even if it dips to 0oC in the greenhouse for few hours... ( of course ill have to pull everything inside if i see -10oC on the forecast ) Then a once danger of frost is over the cold tolerant plants can go in the soil, and the plants that prefer heat will go in the greenhouse and remain in pots in the greenhouse, and only get planted once it's consistently nice and hot outside. ill adjust my plan base on how I see the greenhouse actually perform, I'd be happy to see that the greenhouse slowly loses its heat at night and manages to stay 1-2oC above outside temps before the morning sun warms it up again. is that a pipe dream!? we'll see!
Mate, I would say that if your greenhouse is heated in some way...then it would be alright. Having said that, I will tell you that nothing goes into our greenhouse before april - may. We use our windowsills for propagation and germination for safety sake. Aside from this--may I ask if your greenhouse has already been placed up next to your house? I am thinking that if it isn't, then do you have another location that you could place it with thoughts concerning light. With the greenhouse up next to your house, you will be missing light from one aspect. On the other hand, it may be a tad less cold. I looked at your plans for behind your home, but could not tell what the orientation is. This project of yours is all so exciting. I am excited for you too and wish you every success. Keep us posted.
@Sjoerd i'm buying some used lights, soon i'll have 6x 4feet florescent bulbs hooked up and ready to grow seedlings. i will start seedling under these light starting March 1st for peppers. the greenhouse is a good 12-15 feet away from the house. the garden is east facing, and as such the sun rises in the back of the garden and then falls behind the house. the greenhouse gets shaded by the house later in the evening when the sun is falling behind the house. not in the best spot possible, but it's in full sun for the most part. it will be heated by a minimal amount of thermal mass (black 2L water bottles, and ill attempt to squeeze input a hot compost pile,( but i have my doubt as to my ability to create a hot compost pile) so basically no heat. I think what i will do is keep some of the plants indoors and some in the greenhouse as an experiment, and we'll see if the plants do better with full sun with temperature swings or low light with a constant temp. I dont think i'd damge any plants, only cold tolerant plants will go in there before the last frost, and even if the temp drops to below freezing, the plants won't instantly freeze and the sun will come back up and worm up the greenhouse soon enough. I think that even if its not optimal, thats whats going to need to happen, because as the plants get bigger they will take up more space and so i'll be wanting to throw some in the greenhouse asap. trying to heat the greenhouse i'll never do, I would just leave the plants indoors rather then have a heater in the green house, I think.
