Supplemental Lighting

After decades of greenhouse growing, relying on the sun for all of my lighting, I'm now back to "out on the deck" and "windowsill" growing. One aspect of the latter that has bothered me is how much artificial light do I need to add to supplement for that coming in the windows, and I figure I'm not alone, so I put together THIS ARTICLE that shows how 1) if used alone, continuous, artificial light should be one-half the intensity of the historical recommendations, and 2) how to calculate the "volume" of light you're getting naturally, so you can determine the supplementary amount needed.

Very helpful. Thanks.

Thanks Ray, useful article. I started with orchids in the fall, and used some of the T5 LED replacement tubes for supplemental light. They put out quite a bit more light than fluorescent tubes. I like them because I can run them up high, and fit dendrobium and other taller plants. They run cooler and use marginally less power.

So, the taller plants were getting 1500 fc and the Phals, Paph, Phrag crowd closer to 500. So imagine my confusion as a new grower, seeing red on all of the foliage of the phals. From 2 tubes, 16” apart on a 24” wide cart, sitting 12-24” above the plants. So now I understand Daily Light Integral, but still had to guesstimate — absent a PAR meter. Overall I was very impressed with the T5 replacements.

Your method is a great illustration of the concept. Thank you for taking the time. Matter of fact, thank you for all of the other information you’ve contributed too. I’m a lifelong farmer and gardener, but orchids — aside from The Cypripediums I’ve established in the yard — are new. Like many new to this hobby (affliction), I picked up a bunch of $1 clearance Onc intergenerics and Dendrobiums. I put 6-8 in semi hydro after a few weeks of conventional growing/watering.... lots of new growth, and clearly I’ve been underfeeding them. Especially the vigorous ones. But between the semi hydro group, “seedlings”, various mature genera, I have not gotten a feeding system down. My well water is 110 ppm at 7.0 pH. Might have to pay to have it analyzed before I kill this P. Besseae. Have resisted RO since I’m already maintaining a water system with overall good water. But I’m off topic.

Anyway, big thanks, and hello from Asheville. My wife’s grandad had a place at ocean isle, and Ive worked in Ag down east there.