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are cool lights cool?

Posted by yoyo27983 Eastern NC (My Page) on
Thu, Feb 16, 06 at 19:19

I have one t12 twin bulb overdriven 48" fixture using 2 cool white bulbs. I have two pepper plants that are 2" under them that don't seem to be growing, only one inch tall with 2 leaves. Are the cool bulbs the problem? Do I need to mix in a different bulb or change both out to something different? Can someone shed some light on this for me?

Follow-Up Postings:

RE: are cool lights cool?

Your bulbs are probably fine for now, until the plants get bigger. What kind of temperatures do you have where the peppers are? How big of a pot and what type of soil are they in?

RE: are cool lights cool?

They are in a 5 inch pot. Temps have been ( guessing) at night around 45 and higher in the day, the light puts out some heat and I have a thermometer now but it is hard to get a good reading. The top of the light gets to about 110, but under is somewhere around 60-70. They haven't grown one tiny bit since they hit the 1 inch mark.

RE: are cool lights cool?

  • Posted by zink 6a (My Page) on
    Fri, Feb 17, 06 at 21:18


Cool white bulbs are really an excellent light source for starting plants. The light quality is not the problem. However, you ought to consider moving the light a little bit further away from the plants. They may be too intense for young plants at the distance you have them hanging. Another recent poster also had starts too close to overdriven lights, with unfavorable results.

Even though I am the person in this forum who posted a lot of info on overdriving, I, myself, do not use overdriven lights on very young plants. They seem to saturate easily and appear to burn if they are too close to the lamps. I have a homemade 6-bulb fluorescent fixture with cool white bulbs that are not overdriven. I hang it about a foot above my starting plants.

Your peppers may be growing very slow due to the low temperature. If this is true, then you might be careful and not allow the starts to get too wet. That tends to suppress the uptake of mutrients and stifle the growth.

You could move the lights higher, and leave the lights on for 20 or more hours, maybe even 24 hours, if you can. This would lessen the intensity, and make the overall average temperature more favorable. Young plants can be lit for 24 hours a day without any problems. Only when they get older do they need a light/dark cycle to stimulate their particular blooming phase. Some plants require 12 hours of dark just to activate blooming, but can easily exploit 24 hours-a-day when young.

What color have the leaves been? Did they start out green and change color as they seemed to stop growing, or has everything just stayed the same - just not changing?

Good to see you back in this group, as of recent. Your wisdom and experience have been missed. I remember it wasn't your style to mess with electronics(or goofing up a perfectly good lamp). Keep posting.


RE: are cool lights cool?

Zink, thanks! I'm not mechanically inclined whatsoever. I want plug-n-play! Wiring scares, er, intimidates me.

I hadn't been posting much as the forums were unbearably slow on my dialup, then I had computer problems with BOTH computers, then my work and personal life just got amazingly hectic. But all is well for now and I'm back.

RE: are cool lights cool?

Zink the color is a nice solid green color. I think they have grown just a tiny bit now. I put them in the window for a hour of sunlight also. Didn't want them to get spoiled, so after about an hour, I moved them back to the light. I thought the light could be real close without problems? I have another one I started in a mouthwash cup and it is in a window that gets sun all day. I will see if it out does the shop light plants. They are all cayenne peppers.

RE: are cool lights cool?

Regular T8/T12 fluorescents need to be nearly touching most seedlings (most seedlings like full sun). With some older inefficient tubes, particularly the larger T12s, even this was a little less ligh intensity than ideal. With modern efficient T8s, a couple of inches is plenty close enough. With some tubes/plants, and definitely with overdriven tubes, you will need to move them further away.

Having to move further away is good in many ways. It means that the plants are getting enough light (because closer is too much) and also you will be able to grow taller plants. A tube that needs to be almost touching the leaves is only good for growing plants a few inches tall. If the tube needs to be say eight inches away to avoid burning, then you can grow plants a foot tall or more without losing the bottom leaves.

RE: are cool lights cool?

1. Pepper seedlings are much slower growers than tomatoes.

2. Do you use any fertilizer on them? If you use starter mix - it has about none. It is sterile - so you do not get any fungus - but it runs out of fertilizer in a hurry.

How about a weak solution of fish emulsion?


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