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CFLs as grow lights?

Posted by saood Saudi - 10b (My Page) on
Tue, Oct 22, 13 at 5:00

I bought six 20W daylight CFL and am keeping it each one over one 4" pot - having 3 seedlings. The CFLs are like 1-2" above the seedlings. Using a light meter I measured the approx. foot candles being hit around the top of the seedling and it seemed to be around 2500-3000 fc. and I could sense that they generate some heat around near to the bulbs. The temperatures reading near the bulbs are 5-7F higher than the normal room temperatures. I was reading on one of the FAQs on GW that seedling require 750 fc and also it is advised not to expose them to direct sunlight (or even windows getting direct sunlight). Now I was thinking if I should maintain this distance or increase it so that the foot-candles reading is more closer to 750 fc? Is the 3000 fc reading too intense for the seedlings?

Would highly appreciate your inputs.


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RE: CFLs as grow lights?

  • Posted by digdirt 6b-7a North AR (My Page) on
    Tue, Oct 22, 13 at 10:39

Have you checked out all the information about this and your other questions posted over on the Growing from Seed forum here?

That is the forum that was specifically created for the discussion of all growing from seed issues so that the gardening forums weren't inundated with seedling issues. And there is a good FAQ there all about the lights recommended to use and how to use them.

Plus GW has a Growing Under Lights forum too that discusses in great detail all the differences in the various types of lights available

Now I was thinking if I should maintain this distance or increase it so that the foot-candles reading is more closer to 750 fc? Is the 3000 fc reading too intense for the seedlings?

The 750 fc recommendation is a minimum. More is better. When "more" becomes "too much" all depends on the age/size of the seedling. Young just emerged seedlings can get burned but seedlings with true leaves thrive in more. So there is no "one for all" setting. It has to be adjusted frequently.

The ambient temps created by the lights also must be considered. Excess heat generates leggy seedlings too so it is a balancing act between enough light and too much heat.

Dave

Here is a link that might be useful: Growing from Seed forum


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