length of lighting for seedlings

west9491(6)March 5, 2008

i read somewhere that it is recommended to give seedlings 17 or 18 hrs of light, my coleus seedlings aren't growing, and i think i got them on 12 or 14 hrs, think that s the prob?

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maineman(z5a ME)


Because coleus seeds are so small to start with, it takes the seedlings a while to "take off". During the early phase of plant growth, the growth rate is proportional to the plant size, so tiny plants grow slowly at first, and then speed up progressively as they grow larger. Then it becomes time to think about nutrition.

I think your day length is too short. Some people actually leave their lights on all the time at first. I usually set my timers at 16 or 17 hours of light.

Another thing to think about is the temperature of your growing medium. It might be a good idea to measure that with some sort of thermometer.


    Bookmark   March 6, 2008 at 2:30AM
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Coleus needs to be sown on the surface. They need light to germinate. If you covered them too deeply they will not germinate. I use a quality heat mat WITH a thermostat and a propogation bag (fancy term for plastic bag). I have it set at 78 degrees. I get all my seeds to germinate is 2-5 days.

    Bookmark   March 6, 2008 at 10:19PM
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they've germinated, so that's not the problem, that's as far as i can get, they get their 2 little cotyledon leaves and stop, like i said, they're over a month old and haven't done a thing......

    Bookmark   March 7, 2008 at 11:12PM
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nygardener(z6 New York)

Could the growing medium be dried out? That happened to me with a lot of seedlings last year; the surface looked moist after watering, but water was just wetting the top half-inch and then draining. I put the flats in an inch of lukewarm water until the water wicked up to the top (10-15 minutes) and they immediately started taking off. I needed to repeat this routine every couple of weeks.

    Bookmark   March 12, 2008 at 12:01AM
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