I'm starting an indoor garden, b/c I live where its constantly cold, and snow/freeze danger doesn't go away until late May. I have purchased a plant sprouting system, as well as a heat mat, some containers and a plant light.

I'm having an issue with heat though. Inside the thin plastic sprout container, the heat mat can get through and supply heat. However, the other containers are too tall for the heat to travel to supply heat to the plants. I plan to keep the plants inside the sprout container for a bit, but its cold in the room I'm doing it in. I have a old halogen lamp that get very hot, but its a fire hazard; I can't leave it on for more than an hour.

I don't want to invest (or hang) a large heat lamp array from my ceiling, nor put specific bulbs in my ceiling lights. I have looked on Amazon to find a small lamp (like a desk lamp) that can just sit next to the container and supply heat from above.

Should I get another (stronger) heat pad? Any other suggestions?


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    If the temperature is not below 50 °F / 10°C it's fine, plant-wise. If it is lower than that, apply more lights that mainly produce light (and some small amount of heat as a side effect) - presumably efficient plant-lighting LEDs these days (I've yet to upgrade my old fluorescents, but that's were I'd go next when I do) since indoor gardening almost always needs more light.
    – Ecnerwal
    Commented Apr 8, 2022 at 11:20
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    There's a surprising lack of any "up to date" (LED plant lighting has come a long way) questions/answers in a look at the search, but this one from 2015 is still pretty good reading. There's very good stuff (greenhouse-scale very efficient) available "off the shelf" these days. gardening.stackexchange.com/a/16272/6806
    – Ecnerwal
    Commented Apr 8, 2022 at 11:38
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    get a dimmer for your halogen light to run it cooler. A cheap gentle warmer is a fish tank heater and a fish bowl with a lid, no need for fish.
    – dandavis
    Commented Apr 21, 2022 at 8:20

1 Answer 1


Seeds only need warm temperatures to sprout, you want low temperatures to grow or the plants get too tall. Some years ago I grew my own vegetables and flowers in northern IL, west of Chicago. At that time I used 48' fluorescent shop lights with a few added incandescent bulbs. They were in an unheated, poorly insulated 2 car garage. The lights provided some heat. In a home I think heat could be a problem. I did not measure, but the likely lowest garage temperature was about 40F and average of roughly 50 to 65F. My lights were just above the plants and an occasional leaf got burned by touching a bulb. I raised lights as the plants grew. It worked fairly well. I sprouted seed at about 85 F in the house. Halogen is a good color light but it would need to be on 8+ hours. As I recall, my lights were on 24 hours. I have not kept up with light technology but I have several LED fixtures for aquariums that do well. There are also compact fluorescents. You will find many options searching aquarium lights.

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    Yup. One they've sprouted, keeping the temperature down is the main problem, especially with a lot of lighting throwing heat. Doubly so if you are growing to transplant into the garden eventually. You DO NOT want a heat lamp or halogen -you'll cook your plants. Best I recall 24-hour light is not a good idea. I have friends who did that with their seedlings and it was not a good year for them.
    – Ecnerwal
    Commented Apr 8, 2022 at 2:22

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