Stunted Growth: Too hot?


We got a greenhouse this spring, and I started some seeds in early/mid May. They sprouted quickly, but after a couple of weeks they were a pale green and only had their initial set of leaves. My concern is that green house was getting too hot and I was over feeding too early. I had a similar experience with all the other seeds (tomatoes, peppers, etc). I have removed them from the greenhouse to an outdoor location that gets full sun, but they don’t seem to be recovering. Any thoughts?


What soil are they in? I suspect the soil is way too “hot” with nutrients that burn the roots of the new plant. They actually need to be in something designed for seedlings like a starter soil without nutrients.

It’s possible you could gently remove them from their current pots and transplant into a milder soil. I would get as close to the plant as possible without disturbing the roots.

Over watering and wrong PH are the other factors that you need to be watching.

If these are autos, you might not get much from them.



That soil might be too acidic with all that wood mulch in it breaking down… However I am leaning more towards the clay pots… they get hot in full sun and most plants do not like their roots cooked.

Take them out gently keeping the roots, but leave that soil for something else like veggies later. Get better soil for cannabis and cut it with some seedling starter mix to keep from burning them. Replant them into cooler containers and maybe even give them a little shade screen to filter the sun to help them recover. Check your water ph as well.


It’s pretty basic porting soil (added nutrients). I started them in paper seed pots, and transplanted them to the clay pots when I moved them outside. I will get them out of the clay pots.
If strong nutrients can burn the roots, I bet I started feeding too early.
I don’t think over watering is the issue.
Thanks for the input.


Oh, not at all! Most of us have done the same thing; myself included.

If you do a little research you can find a good soil at your local nursery or Big Box store: just look for things like bat quano, kelp, things like that. If it says “moisture control”, avoid it. A lot of folks use the Fox Farms products but some of them can be too hot for seedlings.

I usually start in a media like coco or Promix and only water until the first two leaves (cotyledons) start to yellow. At that point I can decide how they will be planted.


@Doncos23 How old are the plants in the pictures?

And welcome to the forum!!


About 6 weeks. Based on the input above, I have transplanted them into cooler foam pots and moved them to slightly shadier place.


I apologize; there is a mis communication I think. What I meant by “hot” soil was one that was too rich in nutrients and fertilizers for your seedlings to handle and the roots are getting burned chemically.


I think Doncos removed them from the soil and placed in different soil… I hope.

The extra feeding I believe stopped too, but I said to replant into cooler containers. The small clay pots will over heat the soil in full sun.


How hot does it get where you are? My little plants thrive in the 80-90 degree sun. I use fabric pots as they stay cooler, using clay pots is not good. And I never feed them until they have five or six nodes. You might have to start over with better pots, a better soil mix and more sun.


You said you fed them? They will not need any food or nutrients until your first 2 feeder leaves yellow and die they start with a c. But I can’t spell lol


I have stopped feeding, and replanted in cooler pots. I tested the soil yesterday and it had a neutral pH (right at 7.0). At this point things look better. I also started another set of seeds (not feeding and in cool pots) they have sprouted and are looking good.
I live in Southwest Colorado at about 7000 ft. The temp these days is in the high 80s/low 90s, but it was getting well over 110 in the greenhouse.
I will update as things progress.
Thanks to everyone for the great advise.


Did you use a soil with less nutrients? Until that happens they may struggle. Heat can definitely retard growth but what I’m seeing is some kind of lockout or nutrient issue.