When to move seedlings from 23 Watt CFL to 400 Watt MH?

Curious as to how to tell when a seedling is ready for the big lights, as well as what height from the plant to start the light at...

I have read a number of conflicting posts, ranging from people saying you can use a 400 Watt Metal Halide from day 1, and others say to wait 2 or 3 weeks after sprouting...

The light is in a very well vented 5'x4' room, and I can keep the temps at a constant 75F all year round, so excess heat will not be an issue.

Can anyone give me some advice or their personal experiences with this?

Thanks!

I start my guys out in a 400HPS, granted its a way away and gets closer as they grow.

I start mine pretty early, but you don't have to. Sometimes I have them under CFL's for 2-3 weeks, and then move them over. I usually like them to have at least 2 sets of leaves. CFL's are good for veg in general because you can keep the light very close to them with minimal heat issues. This will promote tighter node structure than MH and will produce more bud sites per inch of plant. The only real drawback is that the plant won't grow as quickly because the CFL doesn't penetrate like the halide. So either MH with faster growth and highter heat(which is fine if you can deal with it) and expediting the whole process which is desirable for a lot of people, or CFL with a little bit slower growth but tighter node structure, and almost not heat.

2-3 weeks under CFL, and then under a MH or HPS hanging about 18 inches above the plants as long as you have them cooled.

You know, I was wondering... what about using a combination of CFL's and the 400w Metal Halide? I have several CFL bulbs with work light clamps on them, that I could attach to the side of the pots to help side lighting, and getting light to the lower leaves that normally get little light penetration. Would this be beneficial? Again I can keep the room adequately cooled (pulling cold Michigan winter air from a window outside of the grow area and venting it back out with a 462CFM 6" inline fan that is on when the lights are on).

i went 2/3 weeks under cfl until my plant were around 6/8 inches tall, then got them under 600 watt hps. personally i will always start cfl coz u can hold the light 2 inches awaywith no heat issues at all. u gotta hold ur big light too far away and ur lil plants are gaunna stretch too much( well it bloody well did to mine). unless u'v got a cool tube even if ur area well vented i would still be surprised if the temp at plant top wasnt a bit high. and i'd also continue with your cfls at the top at first until your foliage is real bushed b4 u move them too the sides. more light the better.

I start my seedlings under a 400w MH at 3' away and move the light down 1" a day untill it's 12"-18" away. I also have a cooltube and temps are 75-78 all the time. I don't really have a problem with stretch.

dura72 said:

i went 2/3 weeks under cfl until my plant were around 6/8 inches tall, then got them under 600 watt hps. personally i will always start cfl coz u can hold the light 2 inches awaywith no heat issues at all. u gotta hold ur big light too far away and ur lil plants are gaunna stretch too much( well it bloody well did to mine). unless u'v got a cool tube even if ur area well vented i would still be surprised if the temp at plant top wasnt a bit high. and i'd also continue with your cfls at the top at first until your foliage is real bushed b4 u move them too the sides. more light the better.

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How do you get them so big so fast??? all stock?? when I start my seedlings, after 2 weeks they are only an inch tall with 2 sets of leaves, I use T8 Redi Grow lights 2 inch away from sprout. Mind you mine are white widow, My seedlings one month old are only 2-3 inch high with 4 sets of leaves very close together, they are now under 400 watt MH watering with root grow and super vitamins light mix, and nutes light mix every second watering or once a week.The light is close to 2 feet away from plant with cfm fan on constant to cool light and also room fan to strengthen stalk. temps at 74 daytime and 68 at night, 18/6 light schedule. Always watch for light burn , can shock the lil fellahs with too much light too early!