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I've recently purchased 3 dwarf citrus trees that we plan to keep indoors for ~9 months of the year. We are in zone 6 so we can only reliably move the trees to the porch for June, July and August with time moving in and out in the spring and fall for acclimation.

The trees will be kept in 3 different rooms, all of which we regularly use. The individual trees are Dwarf Meyer Lemon, Dwarf Venous Orange and a Dwarf Key Lime.

Current available lights are 6 300 watt max can/spring lights that mostly have 100w equivalent 1600 lumen leds on the 5000K spectrum and then I purchased 3 200w Comp Fluorescent lights that initially will be running 6400k 200w lights that, on the safe side, we will estimate at 13,000 lumens. These lights will all be custom mounted on an adjustable bar and kept a little less than a foot from the top of the trees as they grow and be put on timers for 14-16 hours a day. Combined this calculates out to ~58,000 lux per tree given a 3'x3' area, using 2 can lights and the 1 compact fluorescent.

There will be very little window light access, maybe only a few hours a day from a southern facing window. I'm loath to do anything extra special on the color spectrum, since these are rooms we regularly use like the kitchen/bedroom/hallway. While I can direct the lights so that they are not at risk of shining directly in people's eyes, creating such a bright room that we would not want to sit near it without sunglasses isn't optimal either.

Questions: Is my current plan sufficient for light? If it is not, what is the most cost effective way of making it sufficient? Do any of the 3 have greater light requirements than the others?

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    Do want healthy growth or growth and fruit? – kevinsky Mar 30 '15 at 10:56
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    @kevinsky Healthy growth is the main goal. – Anubis Mar 30 '15 at 12:19
  • Don't know. What does the plant say? Is it growing? Is it lengthening spaces between internodes? If so then it maybe stretching for light. – nportelli Mar 30 '15 at 15:04
  • @nportelli I'm preparing the areas before the plants arrive, they should get here sometime in the next week or two, by mounting lights setting up the timers and buying nesting pots to grow them in. I was hoping to get enough information to help minimize shock or a prolonged period of hampered growth. – Anubis Mar 30 '15 at 15:28
  • Ah. I don't think lumens matter so much as spectrum does. Hence why the newer LED grow lights are a red/blue spectrum. I've not tried growing under can lights or CPF's. I have an old MH light from my aquarium that I use. – nportelli Mar 30 '15 at 15:40
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I don't know the specific requirements for those trees. However, that should be way more than enough for a nice leafy citrus tree if my 20-year-or-so old grapefruit tree is an indicator. We usually just give it as much light as the houseplants get, and it does well. However, it is rather slow growing on that light, but it's still nice and green and looks great. It's never been spindly, no matter how much light it's gotten. Light mostly seems important for growth rate, with my tree. I think it would just stop growing at all rather than get spindly, if the light were that low. It has gone probably weeks to months without growing before, but it tends to grow more when it gets more attention.

I gave my grapefruit tree somewhat more light a few months ago (because I put grow lights in for my garden plants). It's in my room a few to several feet away from some lamps (no shades) that have 23 watt CFLs in them (three bulbs; two 6500k and one 2700k). The tree is growing much, much faster. The light mostly hits the top of the tree. Technically, there are several CFLs lower down, but the mylar blocks most of the light from those (not all, of course). There's a bit of sunlight coming through the window, but not much. Your setup has a lot more light. You should have thriving trees in no time, if all you want is leaves, unless your citrus trees are different than mine. I grew mine from a seed from a grapefruit that I ate in the 1990's.

If you want flowers and fruit, too, I recommend giving your trees more red light. That means, lower color temperatures. Blue (which is found more in higher color temperatures) is great for leaves. I've never given my grapefruit tree much red light. That may be why it's never produced flowers or fruit. You may also want to give them more potassium and phosphorus, if you want fruit. Typically, my tree has probably only received 24-8-16 fertilizer, and only rarely. I'm trying out other stuff, though. I gave it some potassium sulfate a few weeks ago. That may also be influencing the extra growth, but it was already growing extra before then.

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