Grow Light Informations

Photosynthesis does not use all the Sun's light, but only the extremes of the visible spectrum, blue and red. The center of the spectrum, green, is reflected by the plants, which gives them their color. The blue wavelength promoted leaf growth, while the red, stem growth. For starts, leaf growth is what matters, since the seedlings are exhausting the seed food reserve to grow leaves and produce photosynthesis.
The light spectrum of the grow light is therefore important. I made some research on the lights I bough.


There isn't enough energy in the short wavelengths. The grow light setup currently has 2 tubes, and will soon have 6 tubes in a 3x2 setup, with ~ 2-3 inches separation between each fixture. That gap is enough to fit a line of blue LEDs in between and gives a useful boost.

Here are the full specifications on the Ecolux lights used in my setup:

• Part#=49893
• Initial lumens=1900
• Color temperature=3100K
• Color rendering index=90

Next step will be the design of the LED lights.

Grow Light Setup, Finally!

Today I got a grow light setup installed in the garage. I used two GE Ecolux T12 tubes, and a 4Ft 2-light shop light fixture. It is barely wide enough for the trays, and I may have to add a second fixture. The shelf is wide enough to set the trays lengthwise, so by setting three 2-light fixtures (6 tubes), I could have 4 to 5 trays in there. Each tube is 40W, so that would suck 240W. We will see how the single fixture works with those spindly beans first, if they survive, then I may go for a 6-tube setup. For now I use a timer, and will keep the lights on during the day, but with a 6-light fixture, I would use a light sensor to turn the lights off when daylight is strong enough.
This is my first grow light setup, and it is exciting!

Looking online in the "medicinal" industry, I see numbers between 1500 and 3000 lumens/sqft for indoor only plants. In this setup, the starts are next to a South facing window, and get a boost in lumen and spectrum a few hours every day.
A seedling tray is 1.4sqft, and therefore needs between 2000 and 4000 lumens.
Each fluorescent tube is 1900 lumens. The growing setup must have between 1 and 2 tubes per tray. The current setup is on the low side. A setup with 3 fixtures, 6 tubes, for 4 trays, would be adequate.
If the current setup gives satisfying results, then I will install a 6-tube setup with 4 trays.