[laughingwillow]

MH, I'd guess.

HPS runs through mainly the red spectrum, MH the blue. HPS does a good job recreating end of the year light, conducive for flowering. MH is a broader spectrum that promotes vegetative growth.

lw

[laughingwillow]

I'm afraid you would prolly have the best luck using the MH lights as a suppliment to natural. To grow by artificial light only and maintain normal growth may not be possible. But I would prolly start experimenting in the 100-200 watt per square foot range under the assumption that it may well take more than that. Keep in mind bulb lifespan will come into play at least a couple times a year. I'm guessing one could prolly get by with 12 hours of light/cycle, as most cactus of interest have evolved fairly close to the equator  under similar natural conditions.

Keep us posted as to progress, eh?

lw

[winder]

You can buy one type and convert to the other with a kit.

Go to the littlegreenhouse.com on the web to find conversion kits and even combo light kits, which will allow you to run 1 of each individually or simultaenously.

Edited:  Didn't mean to create a direct link.

[laughingwillow]

Conversion bulbs generally are less efficient than regular issue, unless there is an inexpensive way to actually create a switchable ballast allowing for the use of standard bulbs of either variety.

windey: Are the powers-who-be allowing hot links to vendors now?

lw

[winder]

LW:  You are correct to ask, and I am uncertain.
Edit to be made.

Edit:  Edit of prior post made.

[EA-1306]

HPS are very effective for growing cacti indoors.

[Green2Herman]

HPS work great. Just dont put them to close to fast or they get black burning.

San Pedro you can give water twice a week if you keep them under HPS. In this case they tend to grow very fast. Some more blue side light like some fluorescent lamps.

I havent tried growing cactii under MH, but that probably works good also. I dont really think it differ much.

[crow]

Roach, whether you go with HPS or MH, I'd go MH as its more for veg. growth, but either way get a bulb in the 400MH or 430HPS range the smaller ones aren't that great and the larger ones would be overkill.

[EA-1306]

I use 2 150 W HPS, and they give me very good results.

[laughingwillow]

.....Right on, crow. 400's are easier and cheaper to come by than 430's. And the cost/lumen payoff is definitely worth considering. Units between 400 and 600 watts are said to be the most cost effective choices, from what I've read.

lw

[anti-light]

shit... i found that a 70w hps works great as cacti over wintering light.... and to start seeds.... and veg sickly cacti.... dry em out if needed.....



the mh is better for all round though...... ive always been a fan of the cool spectrum mesophylls (chloro like sugars)


but im thinking the hps will work fine....the cacti will adjust themselves over time

going back and forth.... inside then outside and vice versa.... will probably make em grow slower though...


take care yall

[EA-1306]

.....Right on, crow. 400's are easier and cheaper to come by than 430's. And the cost/lumen payoff is definitely worth considering. Units between 400 and 600 watts are said to be the most cost effective choices, from what I've read.

lw

I have read that too.
150W HPS are just so readily available, a 600W HPS with a horticultural bulb would be the way to go IMO.
From what I have read horticultural HPS give better results that MH or even horticultural MH.

[Green2Herman]

I dont think the differance are as big as for example growing  very green and fast growing herb (like the famous one). Although maybe the sun in the desert are close to the HPS.

[laughingwillow]

The sun in the deserts are closer to the MH spectrum than HPS. The red spectrum of the HPS simulates the light conditions of late fall.

If you want to pay the price for a full spectrum HPS, that's prolly the way to go. Of course, you are prolly looking at $75/bulb or more.

lw

[EA-1306]

Results speak louder than solar approximation. Much of the solar spectrum is not used by plants. The idea is not to imitate nature, but to provide optimum conditions.