Grow Lights

Submitted by HeLP on

does anyone have experience using led grow lights for seed starting-am weary of using flourescent bulbs


Submitted by HeLP on Sat, 01/19/2019 - 04:03

still hoping for some input regarding LED grow lights-is anyone here?

Submitted by Shanahan on Mon, 01/27/2020 - 16:45

OP has no doubt made a decision by now, so my comments are for other NARGistas who might be interested. This information is for those of you who already have florescent fixtures and are thinking of switching to LED. If you're just starting out, there are plenty of LED shop lights available home improvement stores. The information on light color and lumen level is still relevant for you, however.

I built a set of growing shelves about 30 years ago using ordinary 4' cool white bulbs in shop-light fixtures. Lights were on about 14-16 hours a day, set 3-5" from the pots, and raised as the plants grew. Some flats were placed on top of a fixture for a few days to get the ballast heat for seeds that needed a boost. This set up was recommended by some university, probably Cornell. I had to replace tubes every few years, because they became too dim for good germination. This year will be different: I will convert to LED. The lights will be on about the same amount of time. I'll need a heat pad, because without a ballast the fixtures are cooler. LED bulbs retain their brightness and last many years.

I've already replaced the florescent tubes in the basement and kid's rooms with T8/T12 LED tubes. They are so much brighter, yet use half the wattage. Why is that? Well, the short answer is that light from the florescent tubes is omnidirectional, meaning the light goes everywhere with about 1/3 of the lumens actually reaching your plants. LED tubes direct the light where you want it. If your old FL tubes were originally rated at 3000ish, you could theoretically get away with LED rated at 1000, but why bother? Tubes rated in the 2000 lumen range are easier to find on line. I use eledlights or superiorlighting, there are others.

Another lighting component is color, ranging from warm to cool, and expressed in numbers such as 4000K. Results from a recent study state that the best light combination is 90 percent red and 10 percent blue. But the purpose of the study was to reduce energy consumption for growing food on a trip to Mars. Not in my plans. The next best light was full coverage LED. 50/50 red and blue came in third. So 4000K or 5000K would be good choices.

Yet another tube decision is whether to buy ones that are ballast compatible or ones that bypass the ballast. The buypass tubes require that you remove the ballast and rewire the fixture. It's easy, so don't be tempted to buy the ballast compatible ones. Your ballast will fail after a while, requiring you to either buy and install a new ballast (if they're still available), or purchase the bypass tubes and rewire. Or buy new fixtueres. You can rewire a fixture in about 5 minutes -- longer if you need to install non-shunted sockets (those little tombstone things at the ends). Information at your online store will help you determine if you need them.

I will be buying 17w 4' T8/T12 LED tubes, 2200 lumens, 5000K for my growing shelves.


Submitted by rodlutes on Mon, 02/03/2020 - 05:14

Thank you for all this information.  I have been wondering about LED lighting for plants and I am thinking of converting my very old flurescent lights.  This will help a lot.