100,00k or 6500k bulbs

cghpndDecember 16, 2013

Quick question....
For growing veggies and fruit I was going to buy the T5HO 6500k bulbs, as I am ordering I seen the 10,000k T5HO bulbs.. Are the 10,000k better to use?

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Hi cghpnd,

Well, I donâÂÂt know if youâÂÂre figuring on growing the plants just large enough to plant outside later or to full maturity, where they would actually start producing their crop. In either case however, I donâÂÂt think you want to use the 10,000k lights. CanâÂÂt imagine what theyâÂÂd be used for unless it would be for fish aquariums maybe? 10,000K probably peaks somewhere in the ultraviolet range and plants donâÂÂt use much of that kind of light. Of the two choices, IâÂÂd certainly go for the 6500K bulbs.

Hope this is helpful,


    Bookmark   December 17, 2013 at 1:15AM
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Natures_Nature(5 OH)

Im pretty sure you should take lumens in account as well. I would get whichever one has more lumens. I did a mix between cool and warm bulbs to get a more complete spectrum, plus i have my setup right next to a south facing window for a little sun. I believe that could make all the difference.

    Bookmark   December 17, 2013 at 12:08PM
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You want the best efficiency, lumens per watt and watts per dollar. Theoretically, the 10k bulbs should encourage slightly faster leaf growth and slightly shorter lengths between leaf nodes. I am not sure how difficult it is to demonstrate the difference. Redder lights (3k) encourage stretching and fruit production. Plenty of people grow plants and fruit their entire lives in whatever color light is convenient. Having enough light is a bigger deal than what color the light is EXCEPT FOR LED. LED can be so narrow band as to potentially be useless to plants.

    Bookmark   December 17, 2013 at 8:19PM
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Thanks for the feedback. The supplier finally answered me about the lights. The 10,000k are used for aquariums. Like for coral and such. I'm not growing that!
I plan to do the indoor gardening all year round until I'm able to plant in ground. The little space I have at my apt is filled with pots of milkweed and other flowers so I'm stuck inside with the veggies.
Thanks for the help! It made me rethink my purchase and it was a mistake.

    Bookmark   December 19, 2013 at 10:16AM
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chilliwin(EU DK 7)

One of my lamps is 6500K, but I did not know much about it when I bought it. I am a beginner and mainly I use LEDs still looking for some good guideline.

I found this information about LUX, however I am not sure it is true or not:

"Lumens are a measurement of how much light energy a light source emits. The problem is that this measurement is based around the wavelengths of the human eye, and NOT the PAR (Photosynthetically Active Radiation) wavelengths. Using Lumens is great for measuring light used in flashlights or office buildings, but completely worthless when it comes to grow lights.

LUX is simply a measurement of how much light reaches a surface (Lumens/m^2), but again this measurement is based upon lumens which is totally irrelevant for our purposes. Legitimate PAR measurements are as follows: PAR watts per square meter, PPF PAR, and YPF PAR. These are, unfortunatly, very hard to measure correctly. Very few (if any) vendors will provide you with these numbers because they simply do not have a way of calculating them.

Any vendor that tries to sell their lights based on LUX or Lumens is just trying to trick you!"


    Bookmark   December 19, 2013 at 6:40PM
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Yeah, if a person wants to be more scientific, or more accurate, and measure only the part of the color spectrum that plants actually use, I guess an expensive PAR meter would be the way to go. However, I think many greenhouse growers and most hobbyists donâÂÂt really feel the need to be that precise. A PAR meter is not cheap :-) and as long as we know our lights contain what the plants need, why worry about the small part of the spectrum they donâÂÂt need.

Also, if a person is curious about the PPF values of their lights, there are conversion factors you can use that come pretty close. A few are listed at http://www.apogeeinstruments.com/conversion-ppf-to-lux/

Really, once youâÂÂre sure the color spectrum of a certain light is adequate for your plants, the focus should be on how much of that light you need. That can be calculated mathematically (pretty close) or measured with a very inexpensive light meter. In fact, IâÂÂd say most folks that grow plants indoors under lights donâÂÂt bother with either one :-) and their plants grow just fine.

Just my opinion of course,


This post was edited by art33 on Fri, Dec 20, 13 at 7:30

    Bookmark   December 20, 2013 at 3:05AM
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It sounds like youâÂÂre wanting to grow vegetables indoors, to full maturity. IâÂÂve never tried that but I would think you might need something stronger than fluorescent lights. I doubt they would penetrate deep enough (when the plants got large) to provide adequate lighting. Unless maybe, you surrounded the plants with some CFLâÂÂs ⦠I guess it would depend on what veggies your grew and how many :-)


    Bookmark   December 20, 2013 at 3:52AM
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chilliwin(EU DK 7)


I do not use PAR meter but I use PAR LEDs lamps. I keep trust the sellers' claim of the wavelength, that is PUR range :-)They are cheaper than my T5 6500K 24W grow light.

Still I keep learning about LEDs lamps, when I bought my LEDs I did not know about the PAR (Photosynthetically Active Radiation) but the wavelength are correct. Furthermore I have found that about PUR (Photosynthetically Usable Radiation). "Photosynthetic invertebrates respond best to light that falls into wavelengths between 400-550 nm and 620-740 nm which is the PUR range." So my LEDs are in PUR range.

Recently I bought 3 more 36W PAR LEDs (GBP 19 for 2 lamps including shipping) and 40W PAR LEDs lamps (GBP25.20 including shipping).

My objective to use LEDs was to start the seedlings earlier for the spring. My last season plants were so nice and I did not like to destroy it so I overwintered them, for this purpose I have bought more LEDs lamps, now they are getting flowers. The plants (chilies) are look healthy but I am not sure about the pods, indoor gardening is so complicated for me as a new gardener.

100,00 K could be better than the 6500 K.


    Bookmark   December 20, 2013 at 1:43PM
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