I agree with mehitabel, You really need to do what works for you, regardless of type of light. I don't use HID any longer, but with my current artificial lights I try to keep them as close as possible to the plants. Some plants within inches, some within feet... Depends on types of plants and strength of light. For example let's talk phals, I have some phals within 2" of 40 watt flouros and I have others at least 18" away from big bertha CFL's (haven't heard or used that term for a while ;-)), and all bloom fine. Same with some of my catts, I have a few (mini's) within 2" of 40 watt flouros that are currently blooming and others (Laelia/Lc.) within 4-6" of the bb CFL's that are spiking. Again depends on what the plants like, the minis can do with less light the L/Lc's like more. I sure didn't put my 'kids within 2" of my 400watt HID when I used it, but then again I didn't keep the majority of them 3'+ away either as the article states. Over the last couple of years I've learned, give them all the light you possibly can until they tell you differently. On a side note: John you should really consider looking at those big bertha CFL's (85 watters), replacing one 400 watt HID light with 4-6 of these and spreading them out a little can make a huge difference in getting maximum light to as many plants as possible. Aesthetics aside, I've seen a huge improvement in my plants since the switch. Mehitabel, with the light mover it may not matter as much, but something to consider if your ever loose the second one. I've been using my 85'ers instead of my HID's for @1 year, no issues at all and all bulbs continue to function fine. Plus best blooming 12 months I ever had in my 6+ years of growing. Energy use is about the same, I may see a slight decrease in overall grow room temps with the CFL's as opposed to the HIDs. My 400 and 250 watt HIDs are sitting in my attic, not sure if they will ever be put back in service by me. Bob

Mesquite can send a tap root down something like 190' at least for one tree some university dug up to see. Caliche can be anywhere say in the 1' to 10' range and be thin to foot or two thick. In general caliche is not a continuous unbroken surface. I would never worry about caliche unless it's a known issue. Let the tree earn its keep and let it find the cracks it can send roots through. It's kind of like the drainage issue...if there's standing water the tree won't grow roots in that area and keep roots higher. As long as we're not talking about a bog the tree will probably find a way. A lot of these rules for planting stuff are the absolute best possible environment. But plants, like people, can handle a less than perfect world. I may have mentioned in another thread, this year I grew Mesquites from seed in a bucket with no drainage, watered everyday, so it was sitting in water. If you asked a 100 gardeners 99.9 of them would say that's impossible. Most of what you hear is just repeated from person to person, there's little actual testing or knowledge. A bit of common sense goes a long way when listening to advice.

Growlights should be a minimum of 2 feet from seedlings. The height needs to be adjustable to compensate for growth.

My town has not only 'set back' rules (you can't have 'living space' within 5' of a property line), but also 'land usage' rules (you can't have 'living space' covering more than a certain % of your total land). Every town is different as to the amount of each of these, some have no rules, some have more rules. You could stop by your town's building dept. and they'd give you the basic rules. From your town's assessor you can calculate your current coverage. Oh - and our town considers the walk out basement (the stairs etc.) to be 'living space,' as per the usage and set back rules. Our neighbor had to remove their walk out "dog house" (enclosed stairs from basement to backyard) to bump out their kitchen - because they were at the usage maximum, so swapped the doghouse usage for the kitchen usage. They now have a bulkhead (? those doors near the ground you pull open) which doesn't count as 'living space.' HTH.