So now that I have my greenhouse up, I've been trying to figure out how early to transplant my plants.

I currently have all of my pepper/tomato plants indoors under lights, waiting for the right time to transplant into containers in the greenhouse.

The nighttime temps still hit freezing this time of year occasionally, but if I wait until after the worry of frost to move the plants, it seems that would be the same as starting the plants outdoors for the most part.


I decided to move a few plants that I had extras of out to the greenhouse just as a trial this weekend. I covered them with another layer of plastic to see if that helps a bit. I don't believe frost will occur at all inside, but the temps do still get low. I've considered a heater, but I think I need a better setup before I do that (heated grow box?), maybe next year.



How do I judge when the temps are right to move plants full time to the greenhouse?

You absolutely need a thermometer. It doesn't have to be fancy of expensive; just get one you can hang on a wall or set on a counter. Something like this would do you - we have several of a similar type. https://www.hubert.ca/product/...
Our greenhouse is heated all winter, both with hot water in the floor and air driven by a fan from the house, so it keeps a pretty steady 65+ degrees F, warm enough for the hydroponic greens.
For tender seedlings, we also built a special tent. I start the seeds in the house (on a bookshelf near the stove) and move then out to the greenhouse when they have their second pair of leaves and look big enough.
The tent has grow-lights that I need to go turn off now - 12-hour day. Underneath, we have heating pads, but they haven't turned on at all this year. They're controlled with a wee heat sensor that goes into the potting soil.

I'll take some pictures tomorrow.

I have a thermometer of course, my confusion I guess is how am I getting an "early start" if the temp is essentially the same overnight as the outside temp.

Maybe the answer to my question is just to find what temps the plants I'm growing can tolerate for overnight lows and either supplement heat or wait until the temps stay above that.

Binford, I put my tomatoes in my greenhouse (planted in the ground) a good month to 6 weeks earlier than I could put them outside; I do cover them for a while with a large, clear-ish garbage bag over a ring-type tomato cage (with ventilation in the top - which is actually the bottom of the bag), and also put a jug of water near each plant, under the covering, which helps keep the temperature more even; other tender plants get covered with Reemay at night.

Even if you don't plant all that much earlier, the temp in the GH warms up much faster than outdoors, and your plants are also protected from wind. It will probably take a little trial and error to find what works best for you.

I took those pictures.


Under the bench are 50G barrels of water. The tent is a bit under 5'X4X31/2'. Heavy plastic stapled to back, top and sides, hanging loose in front, but can be secured. It's about 5 degrees warmer inside the tent than in the greenhouse, and steady, even though the heating pads haven't come on at all. The plants themselves give off enough heat. Once they grow bigger, I'll have to keep the flap open all day, or they'll start wilting.

The wire coming from that pot is for the soil thermometer.



The heating pads (very useful; not that expensive), their controller and light fixtures are plugged into a power bar, separate from the lights over the tanks, so I can keep them on longer.



Greens like it e cooler than the baby tomatoes and peppers. I've been trying all kinds of plants in the hydroponic tank - a squash seems to be doing well, but the cilantro didn't make it and the tomatoes had to be rescued and planted in soil. That was back in December. They're doing all right.

You may have started your tomato/pepper plants too early, but putting them in a cool greenhouse shouldn't hurt them. It will only slow down the growth until it warms up. Make sure they are getting plenty of light. I see you are in zone 6a. I am in zone 6b. I start my tomato/pepper seeds in my greenhouse around March 21st. Our last frost date (varies) is May 15th. By then, my young plants are ready to move outside, although I usually keep most of my peppers in the greenhouse for the entire season. BTW...and you may have done this, I always plant more seeds than plants I need just in case of a mishap, and I lose some.

Good info all, and thanks for the pics.

Looks like next year I'll just start a little later, and put together a heated box similar to Serpent. Ill be able to start my seeds indoors, but then when I transplant to jiffy pots, I could move them all to the greenhouse and not worry about temps.


On the plus side, we had a very chilly, freezing rain/ice "Storm" Monday. Temps were 30-34 all day. I had aligned the plants I had potted up and left in the greenhouse and covered them with plastic before the cold. It shot back up to 60 yesterday, I checked on them expecting wilted, sad messes, but they all look really good to me.

One of the things I respect about tomatoes: they bounce back. Very forgiving. And they like being transplanted. The dogs of the vegetable kingdom: they thrive on attentionattention.
I'll be moving these guys into the large containers in the unheated greenhouse by the end of April. A few might go outside later. Bananalegs and the the red cherries prefer outdoors so they can climb unrestrained. I'll plant some in the bins by the propane tank fence - herbs and flowers didn't do well last year.

binfordw said:
So now that I have my greenhouse up, I've been trying to figure out how early to transplant my plants.

I currently have all of my pepper/tomato plants indoors under lights, waiting for the right time to transplant into containers in the greenhouse.

The nighttime temps still hit freezing this time of year occasionally, but if I wait until after the worry of frost to move the plants, it seems that would be the same as starting the plants outdoors for the most part.


I decided to move a few plants that I had extras of out to the greenhouse just as a trial this weekend. I covered them with another layer of plastic to see if that helps a bit. I don't believe frost will occur at all inside, but the temps do still get low. I've considered a heater, but I think I need a better setup before I do that (heated grow box?), maybe next year.



How do I judge when the temps are right to move plants full time to the greenhouse?

I moved my plants outside last year one week before the last frost and killed almost everything last year was my first year with greenhouse. I got some lettuce out there now seems to be doing ok making plans to heat the thing this winter think I'm going solar. New to this website.

I potted the rest of my veggies up this weekend.

Out of the 6-7 plants I put out in the GH earlier, I had one tomato plant "die", I'm assuming from the cold. The rest of those plants look fine- a couple pepper plants had a few damaged leave spots, but not much.

fritom444 said:
I moved my plants outside last year one week before the last frost and killed almost everything last year was my first year with greenhouse. I got some lettuce out there now seems to be doing ok making plans to heat the thing this winter think I'm going solar.

Best way to go! Can be tricky, though. Read everything you can before buying equipment, and if you can enlist the help of somebody with experience, so much the better. We lucked out with our solar guy - he knows the process inside-out, has good sources and can improvise. He's hunting a deal on new batteries for our system right now.

New to this website.

HELLO!! I haven't been around all that long myself, but met some really nice Toms.

Hello, I'm from Northern Ontario zone 3, I have a small glassed in greenhouse 6 feet by 8 feet, i have already started my plants in doors, I'll transplant from the original seeding pans to larger pots and eventually move them to the greenhouse usually end of April/ first part of May. our last frost date up here is usually sometime around may 24 but we have had a freak snowstorms in June. i have a small basic portable electric heater that is set to turn on at just above 0 celsuis (32f) just to prevent anything from freezing and it works great, the greenhouse heats up during the day and holds the heat but the heater is just in case the temp drops below freezing and damages my plants.

I'll take the plastic sheets off the connecting door between heated and unheated greenhouses pretty soon (Sammy, the greenhouse cat, will like that!), so I can start working over the bins and adding fresh earth in preparation for transplants - probably mid-April.

I've already turned off the floor heating, but may have to put the fans from house back on the next few nights, and close the flap over the seedling tent, as we're expecting colder temps. It'll go up and down for a some weeks yet.

I have a couple of hoop houses here in the Rocky Mountains. In the spring things warm up during the day but often dip below freezing at night. So I start many of my plants inside in March/April and once they get some permanent leaves I walk the flats out to the hoop house every morning and then back into the house at night. That way they get the intense sun and warmth of the hoop house during the day but still remain protected from the frost. Some nights in May, if the weather looks good, I can usually leave them out overnight and by early June we have passed our last frost date so I can plant them in the hoop house permanently. It takes some time but it works for me.

You can increase the overnight temperatures in your greenhouse with barrels of water, stacks of concrete blocks or just about anything else with a lot of mass, even a pile of dirt

Guess I'll stick with the barrels. We paid $20 apiece for them about ten years ago, and most have not moved an inch since the day we filled them. (Don't even want to think about what that's water's like!) We took some out last fall to make more headroom in the center of the space and have not yet found new employment for them.

Well, I believe we are finally done with freezing temps here. Had 5-6 nights I ran the diesel(kerosene) reddy heater on a thermostat to prevent damages. Kept the temp whatever I wanted it to be, although it did leave a bit of a diesel odor. This didn't seem to hurt the plants, so I'll call it a win!

Those plants certainly look happy! I'm hoping tonight will be our last below-freezing temperature (it will be if the Weather Channel's 10-day forecast is anywhere near right).

Even with all the vents open, it was 105°F in the greenhouse on Saturday, so I covered the flat-plate collector, shut down the pumps, and put up shade cloths. Then we got a late-season snowfall.




Nights were still around 50°F inside, so no damage. I've got tomato and bell pepper seedlings for the local community garden/food program, and they look really good. I start them on heat mats under covers, then use grow-lights when they are a couple inches high, so they don't get leggy.

It's hard to keep a step ahead of Mother Nature!

subarctic said:
Nights were still around 50°F inside, so no damage.

What kept the temps up overnight?