Lights and marijuana seedlings

A question I get a lot is what light do I need to put my seedlings under and for how long.

Seedlings don’t need a 400watt MH or HPS light on them. Though if you do use one keep it as far away as possible. Fluorescent lights are better suited for seedlings. They can stay as close as 2 to 4 inches from the seedling ensuring they don’t stretch and get enough light penetration.

A grow spectrum is needed (or best suited) for seedlings. So a 6500K color temperature will work. FL and CFL are basically the same and most used for seedlings. I think about 15 watts per plant should do it.

Now how long do you keep them under the fluorescent lighting. Personally I would say 1 or 2 weeks. Depending on the medium you use. You can up the watts in these weeks.

When roots start to come out of the bottom of your medium its time to transplant.

Any other suggestions?


Great FAQ Claire :slight_smile:

If I may add a tip: After transplanting seedlings; Your T5/CFL area can be used to house a cloning op. Once your seedlings have vegged at least a month; Take a couple cuttings from each, and label them. Keeping them in perpetual vegetative state, until you sex your vegetative plants. Once you identify a “Mother Plant”; You can root and veg your clones under this same set up. I hope this tip helps you maximize your grow room potential :slight_smile:

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How many hours per day do you leave the FL lights on for the seedlings?

Lighting photo period for seedlings under fluorescent lamps, or any lamps would be 18/6. I actually use 16/8 to allow a little early stretching, and to promote a stronger root zone.