Return to the Growing under Lights Forum | Post a Follow-Up

T12 Wavelengths / Lumens

Posted by cmpman1974 (My Page) on
Wed, Dec 29, 10 at 12:38

I do not have T8 fixtures so let's forget that issue right now. I have grown lots of seedlings under fluorescents for years now.

What I'm curious about is whether one believes a Sylvania Cool White Plus bulb (4100k rated at 3,000 lumens) is better or worse than a Sylvania Sunlight bulb (5000k at 2,250 lumens). I put 4 bulbs over each shelf. Are the extra 3,000 lumens more crucial than the wavelength difference?

The difference in cost is $25 for a box of 10 5000k bulbs vs. $13 for a box of 10 4100k cool white plus bulbs.

I don't grow trying to get fruit indoors. I'm big into peppers, tomatoes and tons of other veggies.

I'm just wondering which would produce nicer seedlings if used. I look forward to replies/thoughts.

Follow-Up Postings:

RE: T12 Wavelengths / Lumens

Without a doubt, the 5000K bulbs. My favs are Daylight, which are in the 6,000-5,500K range. They produce much more blue spectrum.

Another "trick" is to keeps the temps as cool as you can, within reason of course. 55-60 degrees will produce short, stocky plants, provided you don't water with high N ferts. Tomato-tone is ideal for root growth and a $6 bag will last for hundreds of seedlings.


RE: T12 Wavelengths / Lumens

Thanks Mike. I didn't know if lumens outweighed spectrum. it sounds like it does not. I have used 6,500k daylight bulbs w/success in the past that put out 2,160 lumens (T12s). Short, stocky is what I go for. I don't need tall plants. Space is important to me. :)


RE: T12 Wavelengths / Lumens


If you're only rearing seedlings and moving them outdoors after they reach a few inches, you should be fine with either bulb. If you were however growing them under lights to maturity, then the proper spectrum would be more important. You can always mix them as well... or shop at another store.


 o Post a Follow-Up

Please Note: Only registered members are able to post messages to this forum.

    If you are a member, please log in.

    If you aren't yet a member, join now!

Return to the Growing under Lights Forum

Information about Posting

  • You must be logged in to post a message. Once you are logged in, a posting window will appear at the bottom of the messages. If you are not a member, please register for an account.
  • Please review our Rules of Play before posting.
  • Posting is a two-step process. Once you have composed your message, you will be taken to the preview page. You will then have a chance to review your post, make changes and upload photos.
  • After posting your message, you may need to refresh the forum page in order to see it.
  • Before posting copyrighted material, please read about Copyright and Fair Use.
  • We have a strict no-advertising policy!
  • If you would like to practice posting or uploading photos, please visit our Test forum.
  • If you need assistance, please Contact Us and we will be happy to help.

Learn more about in-text links on this page here