I have my cacti (6x bridgesii juveniles (5-7 in), and 2 montrose bridgesii's juveniles (~5 in) under 108w of 6500k t5's. They seem happy enough, and have been doing pretty well for the time they've been under them (~2 weeks). Before they were receiving natural light from a south facing bay window, but they definitely took off once i switched them over to 15on/9off under the t5's.
CMH bulbs really are the shit though. They are as close to natural light as your are going to get imho. They also work with your standard HPS ballast system with the phillips retrofit 400w cmh's, and from what i understand cmh's are basically a High Pressure metal halide.
If i had a smaller bulb or was working with larger plants that would make the power usage worth it I'd switch them off the t5's to my 400w cmh without question. Daylight varies in its K rating based on many factors, and i think going full spectrum is the best bet as far as healthy plants year round.
Here's a comparison between HPS and CMH as far as spectral emission-
And 6500k ho t5's for comparison-
When i was using 2 x 400w CMH's to grow cannabis, it worked better than any other grow light I've tried for all stages of growth. Seedling, veg, flowering, always had better results with cmh's vs HPS, MH, or t5's (red, blue, or white). Sadly the bushes me and a buddy grew died when a power failure happened over the winter. Froze the plants solid, and was a real tragedy to find them that way.
That's when i stopped pursuing growing cannabis, or at least while I'm living in this climate.
But back on topic, does anyone have any information on what light spectrum would be best for year round cactus cultivation? Would changing spectrum as the seasons do (like with cannabis to induce flowering) be a good idea?
Ideally I'd like to get a lower wattage cmh (150w or less), but am looking into led supplementation along with the 6500k t5's at the moment. Being that leds only emit very narrow parts of the spectrum, would it be worth it to try and build a grow light with a custom configuration of white, red, blue and uv 3w/1w leds?
I'm thinking of diy'ing a <50w test system with 1w smd leds, ideally having it be adjustable as to what ones are on, and what general k its putting off. They are decently priced when purchased in quantity (smd leds), and if i could get away with something around 50w for under $100, imo it might be worth it to give them something more full spectrum. Building a led light is pretty easy too, you just have to make sure theres sufficient cooling or you'll burn up the smd's pretty quick. Other than that its buying a driver and soldering some wires and getting heat-sinks for the smds. Fairly easy project.
Anyone have any experience with leds and what color works best for cactus?
Is the UV going to be beneficial or just a waste?
As well, in general, would cactus prefer more blue or red dominant setups?
And to shroomtroll- I'd go with the t5's as they spread light much better than cfls. If you do decide to use cfl's, I'd consider using multiple lower wattage bulbs than one big cfl. More spread (surface area on bulbs), and you could throw a few lower k bulbs in the mix to even the spectrum out if you wanted. If they don't work as well swap them out with higher k bulbs.
Depending on the sq footage your aiming for, I'd go with 4-6 23w cfls, and have them in some e27 bases (standard 120v bulb socket) wired together, on a sheet of plywood. Cheap, safe (as long as you follow common sense and have basic understanding of ac wiring), and will spread alot more than one big 125w bulb. Also, you can make a custom fixture that fits your garden/enclosure much better than t5's in some cases. My 48" t5s overshoot my enclosure by ~ a foot and i have to cover it with cardboard to block the extra light that is wasted.
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