Posted 01-26-2003 at 06:30:02
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You're right that the tall spindly plants mean they need more light. We've used grow lights for about 6 or 8 years now, and they help but they are not fool proof.
Couple of hints we've noticed over the years:
Keep the lights adjusted so they are as close as possible to the plants. I usually let mine start to grow into the bulbs themselves before I move them, and then just enough to get the plants out of the bulbs (flourescent bulbs, not the incandescents which are much hotter and *will* burn the plants up). I arrange plants as they grow so plants of similar heights are grouped together and I can keep the lights adjusted better that way.
On a flourescent bulb, more light comes from the center than near the ends. That means, given a choice, group all your plants close to the center. If you have too many, put the taller ones closer to the ends so they're closer, and the shorter ones in the middle where the stronger light will reach them.
A few hours on a grow light isn't enough...it is not a "one for one" replacement for the sun as they just don't have the same strength even if the wavelengths are the same. I usually give my seedlings at least 12 hours a day, and 14 is better. I've occasionally forgotten to turn them off at night, and never seen any ill-effects of 24 hours light.
Temperature is just as important as light for seedlings. Too cool and they germinate very slow, but too much and they seem to get root-wilt very easily under the grow lights. So I use a plastic bag on my seed flats to keep warmth and moisture in just until the majority sprout and then I take the bag off. My basement (where the lights are) stays between 65-70 degrees all winter and everything seems to do well then.