Mike, in my post I said I did not use my lights to 'grow' plants, I said I use them to provide 'short night' response in my photoperiodic plants to postpone their bloom times. For that, I don't need 2K foot candles, I need 20 foot candles. For the purposes of determining the quantity of light your plant is actually getting you can't just spit out the wattage or lumen rating output of a bulb as rated on its package. For instance, a hundred watt, unshielded incandescent bulb, ten foot away from an object will only provide about 1.5 foot candles as measured at that objects surface. That isn't much, is it? So, you can't just say a lamp has X lumens and have that mean much of anything. That's the potential output of the bulb. What you are interested in are the readings at leaf level, measured in lux or light density and that is going to vary greatly depending on how far away the light source is, what design the reflectors are, angles, intensity at various points of the cone of the beam. Yadayadayada. And if you think you are actually doing much trying to supplement the natural light by hanging a few shop lamps from an overhead beam in a greenhouse with a flourescent tube in them............well, it's not going to hurt anything, but it probably has negligible actual benefit to the plant. So, if you are really needing to provide lighting by which a plant will actually grow.........then your supplemental growing light has to be quite close to the plant, or the output has to be considerably higher than you think if mounted from overhead beams. The only way to really tell is to meter it out at various points in a greenhouse. That's why I suggested the poster find out what intensity of illumination leafy veggies really take. If she/he can make do with natural light, it would save a lot of money, and I suspect they'll grow just fine without supplementation. That's why in all but special circumstances where high light levels are absolutely necessary for producing certain plants in a winter setting, most growers do not go the expense of installing supplemental lighting. It's expensive to install and it's expensive to run, unless you are just interested in starting a few seedlings or a very limited collection of conservatory plants.

Jodik says: The coir might look dry on top, but down in the center of the pot, it could be quite moisture-laden! I have found it helpful to insert little wooden skewers carefully into the soil to about root level, and leave them there... I take them out and press them against my cheek to test for dampness... if they feel at all damp, I wait to water... but if the skewer comes out dry, it's time to water. My coir is 4" deep in a closed pot. I put the skewer to the bottom of the pot. When I take it out how many inches of bone dry top "soil" should there be before it's time to water again? Is it 1", 2" or 4"? I just went 10 days without water and only 1" of the top was dry so am I supposed to water this direct sun pot once every two weeks or so to avoid over watering, really? And how much water for my 6" closed pot? I had been watering 1 1/2 cup or so once a week and my plant was fine but I'm now worried that was too much so I'm re-evaluating. I know what conventional wisdom says (water deep, not shallow) but that advice doesn't seem to apply to my situation. Also how long should it be before I see new leaf growth in the summer time (first season outside)? My 18 month old Red Lion so far has only grown new leaves once a year. At potting and at dormancy end.

Mdcitrus, Thank you for the posting and I understand your confusion at all the options! I think you are not alone in your quest for an efficient and inexpensive solution. The problem as I see it is that delivering enough light (in other words, enough light to make them reasonably happy) to more than two or three moderate-sized citrus trees is going at some point to become inefficient with standard fluorescent fixtures. My best guess is that four or six 40 Watt by 4 feet bulbs would provide enough light to quite nicely maintain two or three smaller trees (a growing area of about 3 by 4 feet). But if you are looking to go beyond that point, I think it starts to become harder to avoid the HID lights. The two light sources' respective efficiencies really are that different. Of course, once you start down the artificial lighting road, then you need to employ all the ways you can to increase the efficiency of your set-up. Back in the 1970s when I kept my houseplants under regular fluorescent fixtures, I learned to use white walls and white surfaces to reflect light back onto the plants. This light would otherwise be wasted. Ideally, you could create a small room that was set up to maximize your available light. I too would love to see what people are doing--I had to overwinter one of my citrus trees, a rather large Calamondin, in the attached garage because there was not enough room for it in the living quarters. The other reason I posted this thread in the first place is because I have seen questions about the topic in the forum, and when I looked at the general postings on the subject of indoor lighting it struck me that citrus trees are not the same as small vegetable or flower seedlings or African violets, or similar plants that can do quite well under more modest lighting options. I will check this thread to see if any one replies, but perhaps it is a bit too specialized a topic to generate a lot of feedback in this forum. I hope your trees get green quickly! Don

One thing to keep in mind is that a very bright plant light generates a lot of heat, especially in a small enclosed space. The lights and electricity are quite expensive, and the ballast makes a noticeable hum. You might do better to grow low-light plants and concentrate on keeping their environment suitably warm (cooler nights are usually best), well-ventilated, and not-too-humid-but-not-too-dry. Start simple. One or two 75-watt full-spectrum light bulbs, of the kind that are sold for SAD, would be enough to make the space feel warm and sunny to you, would be cheap to run, and wouldn't fry the plants. If the greenhouse isn't fully waterproof, make sure your light fixture and wiring conduits are; this is a good idea anyway. So is a GFCI (ground fault circuit interrupter) outlet, which will shut off automatically in case of an electrical short.