ok, i finally went to wal-mart and grabbed some new CFL's for my indoor grow box.

before, i was using these two large 42 watt CFL's that were very "warm white" light (2700K) and they were hurting my plants...


so i did a bit of research on light spectrum and plant growth. and found out how having only "warm white" light can do bad things to plants.. stretch them out, etc...

so i went out and got 4 of these, (19watt, 1300 lumen for each) and a color temperature of 5000K.



im getting only a little less lumen than i was before, (5200 instead of 5400)
but i think giving my plants a balanced light spectrum is well worth it...

thing is... it seems like they are growing slower.. enough to notice.

so my question is, is 5000K color temperature decent for growing???

Hum, the "daylight" is certainly better than the "warm white". Can you put up some inexpensive T-8 shop lights, with 2-4, 4' fluorescent bulbs per fixture? You can up the K to 6500 and your lumens will be doubled per tube. Some people will use those 4 bulb, 4' fixtures and put 2 or 3 6500K and 1 or 2 4500 K fluorescent bulbs in them for a broader spectrum. I like the 6500 K but anything above 5000K will work pretty well. Those CFL bulbs are just really kind of weak in intensity and you'll need an awful lot more of them to cover much of an area over 2'x2'.

thanks for the reply ken, your probly right about needing more light. but i have them in my 3'x3'
box. the picture makes it look dark.. but its pretty bright in there.. i dont want to go over 100 watts total, because anything more than that is over 5$ extra on my electric bill per month :P

i could upgrade the 4 lightbulbs to 23watt bulbs that put off 1600 lumen instead of 1300, but thats about it, do you think that would help much?

Lining the plywood "ceiling" with tinfoil to reflect unused light would help.

i ran out of foil :P
but i plan on it

Alex, you have done about all you can. Something reflective would help so go ahead and do that. When your plants outgrow that 3'x3' box and you need to enlarge it, just remember to plan on using a 4'6" shop light and go with a 4-tube fixture.

Good growing.

i actually had a shop light, just a cheap one, 4' x2 (two 4 foot bulbs)
it worked fine, then i hooked it up to a timer, rotated the timer a few times to make sure it turned off & on (not too fast)
and it just stopped working, plugged it in to several wall outlets to make sure it wasn't the timer, and nothing..... do some shop lights have some sort of safety feature i dont know about or something?

The inexpensive shop lights have a built-in ballast, and the ballast probably went out. The ballast can easily and cheaply be replaced, but most people (like me) will simply salvage the bulbs and replace the shop light with a new one.

Last spring, I got two new shop lights at Lowe's. I wanted to increase my total lumen output in the "Orchid" greenhouse. None of the two worked. The bulbs would dimly come on but never really light up. The ballasts were defective. Of course both of them were made in China. I took them back and replaced them with practically the same shop lights but from a different company. They worked fine and are still working fine. They were (naturally) also made in China.

I have eight shop lights, all like yours @ 4'x2 bulbs. They are all on timers, so the timer you used had nothing to do with the light failure. I now wished I had put in 4'x4 bulbs. Twice the lumen output but not a lot more expensive to purchase or to run. As these eight slowly fail (and they will), I will replace it/them with that 4'x4 fixture.

It's a pretty sure bet that any inexpensive shop light fixture will come with an even cheaper ballast. And again, it's another pretty sure bet that any replacement ballast will be of a much higher quality. At Home Depot, at least the ones in Minnesota, they only carry American made replacement ballasts. If you shop for a new ballast, it's important to know what kind you need. Although both T8 (more energy efficient) and T12 lamps (less energy efficient) have the same pin configuration, they are usually not interchangeable with any given ballast. If the replacement ballast you buy comes with more wires than your original ballast, there should be directions included on how to hook it up correctly. But it is easier to just get a ballast with the same number of wires as your original. Its best to bring your original ballast with you to the store, so you know that the new ballast will fit into the old fixture. They are not all the same shape. Get a rapid start ballast, not an instant start ballast, if the unlikely option presents itself.


Electronic vs Magnetic Ballasts

--- Both types are directly interchangeable, as long as they are specifically for the same lamp configuration.
--- Electronic ballasts are more energy efficient.
--- Electronic ballasts are more adaptable to different applications and fixture types (i.e. number of lamps per ballast, and series or parallel hook up).
--- Electronic ballasts may produce radio frequency interference if the ballasts operates within that specific frequency range (rarely problematic).
--- Electronic ballasts do not hum as magnetic ballasts often do.

Good information, Rick.

sounds good to me ken :P

thanks for the info guys, but for now im just gonna stick with my CFL's..
if i need more lumen output, i can always use 4 of the 42-watt 2700 lumen CFL's.. and actually get the 5000K-6500K this time
that should do the trick.. i will just have to accept the extra 10$ on my electric bill i guess

but once again thanks for the info guys.. its good to know it might not of been my fault that my shop light randomly went out

alex22ccc said:ok, i finally went to wal-mart and grabbed some new CFL's for my indoor grow box.

before, i was using these two large 42 watt CFL's that were very "warm white" light (2700K) and they were hurting my plants...


so i did a bit of research on light spectrum and plant growth. and found out how having only "warm white" light can do bad things to plants.. stretch them out, etc...

so i went out and got 4 of these, (19watt, 1300 lumen for each) and a color temperature of 5000K.



im getting only a little less lumen than i was before, (5200 instead of 5400)
but i think giving my plants a balanced light spectrum is well worth it...

thing is... it seems like they are growing slower.. enough to notice.

so my question is, is 5000K color temperature decent for growing???

Plain and simple no! The way I understand it, 2700k and 6500k are the main color temps for plants. The 2700k(red)bulbs in my opinion were not hurting your plants at all they were actually doing exactly what they were supposed to be doing. You can grow a plant using only 2700k bulbs and more than likely they will grow faster than normal but as you probably saw the stems were thin and too weak to support themselves, am I correct? I thought so. Try adding 6500k CFL and I'm pretty sure you'll be able to notice a tremendous difference, the growth will slow down but the plants will start to strengthen enough to stand on their own and the vegging will grow thicker and greener as 6500k(blue) color temps tend keep plants Short and thick. In my experience with lights a 2;1 red to blue wattage is optimal. 40watts red 20watts blue

Years ago, I published on ATP/NGA an article about light spectrums and light intensity for plants, @ alex22ccc. @Poolguy42 is somewhat correct in general, but not knowing the plant(s) variety that you are growing, there is a lot that can't be said because we don't know what sort of light you really need. Spectrum is only part of the equation. Available lumens is just as important. Notice the word "available". The lumens that those tiny bulbs produce is extremely limited for growing most tropical plants. But as I said, I don't know what you are growing.

Welcome to NGA, Poolguy42.

Just ignore my post, @Poolguy42. that post from Alex is 4+ yr. old and any comments at this point are probably not needed. Heck, I haven't even used a "shop-light" for several years. I switched over to T-5HO and some LED fixtures 3 yr. ago.

Happy New Year.

@drdawg,

Yes, old thread, but still interesting. We are putting in a nursery for our microgreens and lettuce transplants. I have been researching 4' lighting options for our shelving. We will be growing sunflower shoots, radish shoots, pea shoots, and salanova lettuce.

What T4-HO and LED fixtures are you using and/or do you recommend? I have been looking at the obvious places...HD, Lowe's, Amazon.

EDIT: On Amazon, I have been looking at the ones on the BrightFuture storefront. I cannot post the link since I just registered my account on garden.org.

Thanks!

Jason

@jlbrown1

Jason, I am sorry but I don't know the exact brand of those T-5HO, 4 and 6 tube fixtures. Since I have moved to Vero Beach, FL and no longer have greenhouses, those fixtures are all in storage in my equipment shed. I purchased them off the Amazon site though and don't think there was more than a single vendor that had them (but that was 3 yr. ago).

@drdawg,

Even so, I would still appreciate any recommendations you can make from your experience. It seems the most important factor I can see from all of my research is to just ensure it is 6500K or more. Anything else I should take into account besides that and price? :)

Thanks!

Jason

Because I had two greenhouses (and a third, temporary, one built in the fall just for some plumeria), I wanted fixtures that had tubes with wavelengths both for growth (6000-6500K) and blooming (2500-4500K). Therefore, I had a mix of tubes in each fixture. For those fixtures with 4 tubes, 3 were the 6500K and one was the 3000K. For those fixtures with 6 tubes, 4 tubes were 6500K and 2 tubes were 3000K. I actually purchased tubes in the spectrum I wanted, 20 tubes at a time, and thus, could arrange the tubes in the fixtures as I wanted. These T-5HO fixtures come with and without tubes. For those fixtures with tubes, the spectrum should be listed, but if it is not, contact the seller so that you'll know what you are getting.

drdawg said:Because I had two greenhouses (and a third, temporary, one built in the fall just for some plumeria), I wanted fixtures that had tubes with wavelengths both for growth (6000-6500K) and blooming (2500-4500K). Therefore, I had a mix of tubes in each fixture. For those fixtures with 4 tubes, 3 were the 6500K and one was the 3000K. For those fixtures with 6 tubes, 4 tubes were 6500K and 2 tubes were 3000K. I actually purchased tubes in the spectrum I wanted, 20 tubes at a time, and thus, could arrange the tubes in the fixtures as I wanted. These T-5HO fixtures come with and without tubes. For those fixtures with tubes, the spectrum should be listed, but if it is not, contact the seller so that you'll know what you are getting.

@drdawg,

Why the 2 to 1 ratio? I will only be doing sprouts/microgreens and transplants (lettuce, broccoli, etc.). Everything I read states 6500K. I found one article today that had a 1:1 ration of the warm/cool, but yours is interesting at 2:1.