Grow Light - how much better is 4 than 2?

[ladyslipper]

Hi guys, this may seem like a dumb question but why do we need four grow lights? I am using 2 48 inch 40 watt grow lights that is perpendicular to an east/north east facing window. I am growing mostly phals (both species & hybrids) with a few other kinds mixed in.

The other question is do grow lights come in different wattage (like 60 or 80 watts) and would this burn the plants (none of my flowers are close to the bulbs)

regards mary

[Ross]

Florescent "grow lights" are rated by length of the tube (for the most part). T12 shop lights (the 1.5" diameter size) are the weakest in terms of lumens per unit of energy expended. The T5 special purpose bulbs (approx 1/2" diameter) are the most efficient (strongest) in terms of units of energy expended. There is another type (T8) that is mid-way, it has high-output compared to "shop lights" but less than T5 bulbs.

Now on to your question. T12's and T8's only come in circular or 48" (as far as I know). There may be some specialty application lights other than these. T5's come in lots of configurations. They come in 24", 48", compact (wrapped) styles, etc. Is it necessary for 4 tubes? Depends on how much light you need for your application. 4 tubes will be twice the lumens as 2 (obviously). The strength of light can be fine-tuned by the selection of type of tubes as well as how many tubes. Hope this helps. Generally folks who grow under lights base the light requirements on foot-candles for the plants. Typically, Phalenopsis class orchids will grow well under 1000-1500 FCs. Cattleya types, as well as most Brassias, like higher light (2500 or more FCs). Hope this helps.

[ladyslipper]

Thanks for the info...my tubes I believe are the T12 types so by your description are the weakest. So the wattage doesn't count? How many footcandles would 2, 48inch T12 put out? Would you think I should shop around for T8 tubes? My phals now get a few hours of sun each day but in the winter, I will be depending more on the tubes for the light source for the plants. Have you ever seen grow lights that are shaped light spot lights? I had once & thought I could augment lighting with one or two of the spotlights since going to 4 tubes would be nice but probably won't happen in the forseeable future.

regards, mary

[Ross]

Originally Posted by ladyslipper

Thanks for the info...my tubes I believe are the T12 types so by your description are the weakest. So the wattage doesn't count? How many footcandles would 2, 48inch T12 put out? Would you think I should shop around for T8 tubes? My phals now get a few hours of sun each day but in the winter, I will be depending more on the tubes for the light source for the plants. Have you ever seen grow lights that are shaped light spot lights? I had once & thought I could augment lighting with one or two of the spotlights since going to 4 tubes would be nice but probably won't happen in the forseeable future.

regards, mary

Actually you can get the newer t8's at Home Depot (etc.) and they take a different fixture. Two tubes should be fine. The t8 will be very much brighter than the t12. Not many 4-tube t8 fixtures around. Lots of t5 4-tube fixtures. In the end I'd recommend sticking with what you have till you can't stand it any longer then go for a new t5 fixture. They come 2-bulb by 48" and 4 bulb by 48" and 4 bulb by 24" combos.

[Lagoon]

I've switched my T12's over to T8's, No question T8's are a stronger output with less heat, A total plus!
Unless your growing catts, Dens, multi's bloomers, some of that nature, then you should be fine with lower lighting levels.

You can always add clamp on CFL's down the road if you feel you don't have enough light. Great source for strong spot lighting.