Distance from T5HO lights?

farming2121March 10, 2014

I am just starting seedlings under a couple T5HO tubes and am unsure how high to put them above the seedlings. They have yet to sprout, but I have read anywhere from 3 inches to 10 inches. Does anyone know what the accepted distance for seedlings is?

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Hi farming and welcome to GardenWeb!

Well, as far as germination, some seeds require dark but for most seeds light is helpful or even required. For seeds that benefit from light during the germination period, the intensity of the light is not really critical. Often times the seeds are under some kind of humidity dome and the light can be well above that dome and still be providing plenty of light until the seeds sprout.

Now once they sprout, then any domes are removed and the lights must be lowered to be very close to the seedling. Generally the closer the better but it does, of course, depend on what kind of lights are being used (you don't want to burn the leaves). I use T8âÂÂs and usually keep the lights no farther than about 2 inches above the seedlings. I do have one T5 fixture and since those bulbs get hotter than the T8âÂÂs I usually keep that one about 3 inches above the seedling.

After the seeds sprout, cool temperatures and plenty of light are important. If you donâÂÂt have enough light, or your growing area is too warm, the plants can end up leggy and with weak stems. Good air circulations is helpful as well. Many folks use some kind of small fan (usually on a timer) that will come on several times a day.

You didnâÂÂt mention what youâÂÂre growing but, whatever it is, I wish you the very best of success!

Hope this is helpful,


    Bookmark   March 11, 2014 at 2:02AM
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SouthCountryGuy Zone 4b-5 SE BC(Zone 4b-5 SE BC Canada)

I agree with art in good air circulation is a must. I primarily use T5HO lights and try to keep them within an inch of my plants. I do have at least one fan per 8 bulbs and double up when ambient temps rise.


    Bookmark   March 17, 2014 at 12:01AM
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Should heat mats be removed after seeds sprout? I leave mine on thinking they will like the warm soil. Maybe thats my problem?

    Bookmark   April 16, 2014 at 8:58PM
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SouthCountryGuy Zone 4b-5 SE BC(Zone 4b-5 SE BC Canada)

mikerond, yes, once you see germination you should remove them. After sprouting most plants will grow studier and stronger at about 65F with lots of light.

    Bookmark   April 19, 2014 at 12:33PM
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