Artifical lights too hot for seedlings???

freefour(z6a S. IL)February 13, 2005

I seem to have a problem on my hands. I started my cole crops indoors (first year under artificial lights) and they seem to be turning yellowish or even brownish. I have them on a stand under two T8 2 bulb shop lights. I have overdrove the lights so they are plenty bright. I place the lights two or three inches above the seedlings for 16 hours a day. They seem to be responding quite well until late this week.

I placed a thermometer under the lights and woah!!!! almost 100 degrees. I think they are being cooked under the light. I tried my second shelf down that has two more shoplights (but they are not overdrove) and it is still 85 degrees!

Everything I have read says to keep them between 60 and 70 degrees F. I do not have a basement or a garage. What are others doing to moderate the temperature under lights? I thought about a fan, but that would be a lot of trouble. Any ideas would be great!



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shrubs_n_bulbs(z8/9 UK)

What kind of thermometer did you use? Measuring temperature under intense lights is tricky. Two different thermometers can give completely diferent readings. You should use a silver probe thermometer to avoid too much heating from the lights. For short seedlings, place the probe in the soil and not directly in the light. Remember that many objects will become very hot in direct sunlight but plants are adapted for this and do not overheat. The most important measure of heat is whether the seedlings are growing well.

A fan is always a good idea. Seedlings grow stronger with ventilation, both because it is cooler and because the air is moving. It also reduces damping off and other disease problems.

    Bookmark   February 14, 2005 at 8:21AM
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jkirk3279(Z5 SW MI)

I've seen fans at Walmart for $9.00.

Hook it to the same timer as the lights and it shouldn't be any trouble. I'm going to get one tomorrow along with another SL15 ballast. Had one go out on me in less than an hour.

    Bookmark   February 14, 2005 at 11:13PM
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