I'm no expert, and could be blissfully wrong, but I am under the impression that the redder of the two (2900 K) would be more useful in blooming, while the bluer (5000K) is more for vegetative growth. Furthermore, to be perfectly honest, I don't really know how good a kelvin rating is for determining which lights to use, because I have plants growing under 2 bulbs at 3000 K, some under 1 5100 K and 1 3000K, all 40 watt CFL's, and some under a single 5000 K (85 w, cfl) and all of the plants look just fine. While the lower K lights look red/yellower, and the others look bluer, thats just how it looks reflecting off of stuff and then bouncing around in our skulls for a while, plants see way differently than people. If that makes any sense.

Get the grow tubes. The bloom tubes will produce less compact growth, weaker spination, and greener lusher bodies, not a massive difference but you'll notice it over time. Blooming will only happen with sufficiently intense light (and suitable temperatures, seasonal changes, etc. as required by each species), changing the bulb won't make much difference. But ideally you need real sunlight for growing adult cacti, these lights will not be a complete substitute.

Expect to be able to light about ten square feet and still grow cacti reasonably well. Don't plan on growing anything more than a few inches tall though, because you'll need the lights down fairly close to the plants, which will need to be raised up more or less all to the same level.

If you want to grow seedlings rather than adults, they need much less light and are easy under any fluorescent system. Your lights would easily burn most small cactus seedlings, raise them up higher the reduce the intensity.

Thanks for your answers!! I get real sunlight in my main plant room, but I'm not sure if they will get enough direct light during the day. But at least I know which bulbs to go with!! Thanks again

Ross

If you can afford it and have the room, HID lamps are more efficient and are a better substitute for real sun than fluorescents.

Xerophyte, I was under the impression tho that the HID lights give off heat. Am I wrong in thinking that?

Once I get back home on Sunday, I will take two pictures, one of the window in my room and another of the plant room window. From what I've just read about HID, it seems as tho I can keep them much farther away from the plant and they would probably be easy to hang on an angle compared to a large 4 tube fixture. The main plant room has a beveled ceiling, part of which is window. I am a bit worried that I'm not going to get enough sunlight since the plant room faces N,NW and I keep reading and being told that North windows arn't the best and South is prefered.
Thanks again for everyone's help.

HID do give off heat, so a small fan running nearby is important to help distribute the warmth, and the air movement is great for succulents too, but it's not THAT much - it'll help warm up the room on cool days and is off at night anyway.

Even lower wattage HID lamps provide adequate light to keep them a few feet away from the plants themselves. I use a 1000-W lamp to overwinter many succulents in my garage, I keep it 3 feet away from the table, it works well, winter-growers flower nicely so I know the light is strong enough.

N-NW are poor spots for growing almost any plant, let alone sun-loving succulents - South is good except for the summertime when the high sun angle means plants have to be kept very close to the window to get any of the sun. SE or SW are the better choice year-round.

HID lamps produce a lot of light from a small bulb. That concentration in a small area means that the bulb is hotter than a fluorescent tube of the same power, also more of that heat is radiated as infra-red radiation. Because of this and the concentrated light, HID bulbs must be mounted further away from the plants or they will scorch. The effct of mounting distance on light intensity is completely dependant on your reflector arrangement, but almost always the light intensity will decrease with distance, maybe a little, maybe a lot.

Assuming we are talking about metal halides, they are not noticeably more efficient than modern fluorescents. They should be used when you need a more intense light than you can get from a fluorescent tube. You may also wish to use high power HID bulbs for lighting large areas when the alternative would be ten or twenty fluorescent tubes. HID bulbs below about 250W become significantly less efficient, a fluorescent (or compact fluorescent if you need more intense light) is generally a better choice for lighting small areas.

The spectrum of metal halides is neither more nor less like the sun than fluorescents. Standard metal halides and standard (halophosphate) fluorescents have most of their light concentrated in a handful of wavelengths and almost none at other wavelengths. Newer triphosphor fluorescents combine red, blue, and green to provide a somewhat better spread of wavelengths, and the amounts can be varied to produce a bluer or redder light. Specialist fluorescents produce a much wider spread of wavelengths, and specialist (eg. ceramic) metal halides are available that do the same.

HPS lamps are the most efficient but aren't generally used for cacti because of their spectrum. Maybe there is someone out there who uses them? Maybe one of the new "blue" HPS bulbs?

I a couple of the pictures of my windows. The first picture is my bedroom plant window. This is where I was planning on putting the 4 tube fixture.

The other picture's of my main plant room. As you can see the majority of the wall are windows, as well as part of the beveled ceiling. I can't put lights directly over the plants, which is why I am hoping I can find something that can be angled, or even a standing light fixture.

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If the windows were facing south, east or west, you would be in OK shape, but as it is now, it's not that different from trying to grow them in a cave, there's just not nearly enough light, especially along the ends.

Since the heights vary, it will be very difficult to get enough light intensity consistently via fluorescent bulbs. I don't think anything would work better than an HID lamp, you can hang one from the ceiling (assuming you have a beam to use for support) at the point where the glass ends.

Some other issues: the temps will be too warm for wintering most cactus species, but that't the case no matter what; I hope you have shades for the windows because as daylengths decrease in the winter, it will be bright as heck through your window, the neighbors are going to wonder what's going on in there; if you do any sort of office work or whatever in that room, it won't be pleasant with an intense light right above your head.

Do you have any spare room in a garage or basement perhaps? Any chance the plants can be taken outdoors for the summer at least?

Some succulents can be successfully grown under lights long-term but for others, even with the best efforts and intentions, the end result will be weakened plants, so make sure you are willing to accept some failures, even though it may not be evident for a while, and keep that in mind also when deciding on how much money you will spend and how it may affect the interior of your home. It's a big commitment if you want to do it right.

A north facing window gives so little light that you might as well stick your plants in the basement or a cupboard. Seriously, you'll be lucky to get a tenth of what you need just to keep things ticking over for the winter, you would easily waste more than that from your lights shining out the window. Find somewhere that you can set up artificial lights properly even if there is no natural light.

Thank you so much Xero and Shurbs. I was clinging to the hope that with the window on part of the beveled ceiling it would offset the lack of light from the front windows, but I now I know I have to go a different route.

Thanks again so very very much!!!

Ross Wexler