Semi-tech --light spectrum for tomatoes

[Greatgardens]

I've used mostly the original Gro-lux (not WS) over the years and I've had generally good success raising seedlings until I can move them to the cold frame. But I'm always looking to improve... (It's like searching for that elusive "perfect" tomato!) Right now, I use four 40-watt tubes on my starting shelf which is apx. 12" X 40".

Looking through the info on the internet about grow-lights, it looks to me like the combination of my Gro-lux + cool white fluorescent would be better than Gro-lux alone. Or a combination of original Gro-lux + wide spectrum.Or using a combination of ~2700k to 3000k + 6500k would also be a good option.

That would be (I think) cool white + Daylight or warm white + daylight.

Any thoughts on this would be appreciated. And this has probably come up before, so any links would be great, also.

-GG

[Ricky Shaw]

No proof, but my observation is leggy seedlings with the red bands. The more, the leggier.

[ContainerTed]

I use daylight exclusively in four foot T-12 fixtures. After germination, when I see the first real set of leaves, I reduce the ambient temperature down to about 60 degrees F. This has all but eliminated leggy seedlings for me. My little "green room" carved out of the corner of the garage seems to have a good stratification of the temperature at different levels from ceiling to floor. I simply keep moving the seedling trays down.

When stems are strong, I move the seedlings out to staging points where they begin to be introduced to the sun. Yes, there is a lot of moving out and then back into the garage. A bit of a fuss, but I don't loose many plants. Unless I drop a whole tray.

[greyghost]

Search for an old thread titled "lights for starting from seed". There's a response by Hotwired" that I'll copy. It pretty much has the same info I've read on proper lights for growing plants elsewhere. I haven't had time to look but I remember
Hotwired had light spectrum overlays of the best wave lengths for growing plants-more green/blue for vegetative growth and warmer red tones for blooming/flowering stages. I think many of the gro-lux type fall in this range-more for blooming. I have a variety of t8, t12 and some newer Sun Blaster lights with 6500k for starting tomato/pepper/bedding plants.

I found this by advance searching for posts by "Hotwired". Hope this helps.
This was always a topic I found extremely confusing but I'm having very good
success with the lights I have. The t12 bulbs, for example, were very inexpensive at Home Depot. I bought a box of them on-line; they were described as daylight and 6500k was in the description.

(In the last sentence of Hotwired's response, I believe he meant to say
Natural light at 5000k.)

Like Ted, I grow plants in the cool garage and living in the mid-Atlantic, there
are numerous spring days that plants go outside and then back under lights.


Hotwired
Tomatovillian™



Join Date: Nov 2012
Location: Ithaca, NY - USDA 5b
Posts: 242



Quote:
Originally Posted by ChrisK
Cool white fluorescents work perfectly well for starting seedlings and are usually the cheapest.

Chris, I couldn't get your link for U of Alaska to work, but I don't agree with Cool White (4300K) being best, unless you are growing flowers. Then it is ideal. I always used "Natural" bulbs, until I made up a graphic, overlaying Color Temp, Wavelengths, and the Plant's PAR curve. It was a big eye-opener. I'm a retired optical engineer, so I am a bit anal over anything related to light and tend to look for perfect solutions. Unfortunately, with growlights, there are no perfect solutions. Almost anything will work, but some will work a whole lot better than others.

Fluorescent Bulbs are available in 4 basic colors:

Warm White = 2800K-3000K
Cool White = 4100K
Natural = 5000K
Daylight = 6500K

The Daylight Bulb (6500K) is almost perfect for starting plants inside, since the Blue PAR for foliage and plant growth peaks at about 6600K. For Flowering, the Red PAR peaks at 4300K, so the Cool White is ideal for Flowering and the Red-PAR coverage. The warm White bulb spikes in the IR, and has fair coverage of the Red, though not as good as the cool white for flowering. Both the Cool White (4100K) and the Warm White (3000K) have extremely poor coverage in the Blue portion of PAR. The Daylight Bulb at 5000K is the worst because it peaks at the yellow-green point within the PAR curve, an area of the spectrum which the plant uses very little of that color light.

[greyghost]

I looked for the spectrum that Hotwired had posted in the Lights for Starting Plants thread--they've been deleted. I had copied them at the time.

[Worth1]

One thing I would do is not get bit buy the grow light bug.
All you need to worry about is watts and spectrum.
For all vegetative growth all you need is 6500k bulbs.
As for what they call the bulb is a toss up.
Take tow manufactures of a florescent light and one will call a 5500K bulb daylight while another will call a 6500K bulb daylight.
Others have the term daylight and bright daylight
Then there is the term active spaces.
The grow light people dumb it down for you and charge you for it.
I have used and still have some that are GE 48" T12 40 watt daylight active spaces 6500K 2900 lumen lights that work fantastic.
The newer T5 and TB lights work great too.
The T8 will fit in a T12 fixture but a T 5 needs its own.
Here is a link to what I did here.
http://www.tomatoville.com/showthread.php?t=38988


Worth

[greyghost]

http://www.tomatoville.com/showthrea...light=hotwired

[greyghost]

I see the spectrum photos disappeared from the message--a couple up. If
anyone is interested in seeing them, they should be able to be found on the
following website. Click on the upper left choice---starting plants and you'll see some discussion on lights and I hope, the color spectrums. Sorry about that.

http://www.hotwiredgardens.com/pdfs.html

[Worth1]

Originally Posted by greyghost

I see the spectrum photos disappeared from the message--a couple up. If
anyone is interested in seeing them, they should be able to be found on the
following website. Click on the upper left choice---starting plants and you'll see some discussion on lights and I hope, the color spectrums. Sorry about that.

http://www.hotwiredgardens.com/pdfs.html

What are you trying to show us?

The closest thing to the noon day sun is the bright daylight 6500 k lamps.
They are full spectrum lights.
If you have a CD in the house you can put it up to the light and see every color.
There are also places on line you can make a homemade light spectrometer with a CD.

Plants cant see green.

Worth

[Worth1]

Look right by my thumb where the spectrum is broken up.
you can see the bright daylight 6500 K puts out a full spectrum.
Worth
IMG_20151212_56862.jpg

[Cole_Robbie]

Warm White = 2800K-3000K
Cool White = 4100K
Natural = 5000K
Daylight = 6500K

My only issue with these numbers are that they imply that plants will grow much faster under day light bulbs than under cool white. I use them side by side, and I cannot tell any difference in the growth rate of the respective plants under each bulb. That's not to say it doesn't exist, but it's not as significant as those numbers imply.

[Greatgardens]

Thanks for all the input! There is some really good info in here, and especially the Hotwired pdf on plant starting. Of particular interest to me are his color graphs of PAR and color temperature, lined up color-for-color. Nice pdf! Headed to Lowes today to pick up a few 6500k T8 bulbs!
-GG

Edit: Got the daylight bulbs this AM, and replaced two of the Gro-Lux bulbs with those. Wow! sure puts out more (visible) light. Will be interesting to see if I can tell any difference!

[BigVanVader]

Just my 2 cents but my shop lights do great and I'm a if it ain't broke don't fix it kinda guy. Of course since I am broke that makes it less of a dilemma. To each his own though.

[Worth1]

Here is what you couldn't drag off the PDF of hotwireds page.

[greyghost]

Thanks, Worth. There was also another graph showing color at different
kelvin color temperatures also---it's at the hotwired.com website under
"greenhouse tips, starting plants", right under the above graphs. I think it
helps some people to see "blue" for vegetative growth and more "red" for
blooming.

Anyway, like Cole and Van have said, many people get very good results using fluorescent shop lights without obsessing about kelvins, etc. During the almost
40 years I've been starting plants, I've used my husband's shop lights with whatever bulbs were in them, replaced bulbs with expensive grow lights (3500k range-more suited for flowering plants), finally am using just 32 or 40 watt, t8 & t12 6500k daylight bulbs--now have several Sun Blaster t5, 6500k lamps. To be perfectly honest, I don't see a whole lot of difference in quality of my tomato/pepper starts. Maybe because they also are set outside whenever possible. Or maybe I had a mix of bulbs-- So, I'd have to agree with the fellows but for anyone just getting lights, I'd definitely go with the Daylight 6500 kelvin
for plant starts.