Lowest LED wattage

A question from a fellow grower:

what are the lowest led lights I can use to grow with ???

The lowest wattage to grow from seed through flower?

For almost all lights, especially the traditional HID lights, you need about 50 watts per square foot.

For LEDs, T5s and CFL fluorescent lights you can use a little less. mostly because you can have the light a lot closer as they are not as hot as HID (and proximity to the light source dramtically increases intensity due to the inverse square law/property of electromagnetic radiation, this includes light and heat), and so you can get away with about maybe 40-45 watts per square foot with these lights. With a really good LED, one that is specifically made for plants, you can maybe get away with about as low as 30-35 watts per square foot.

LEDs, like any other light come in just about any wattage you can imagine.

Happy growing,


Wondering about keeping seedlings or cuttings alive for a few months or more before flowering.
I just want one plant flowering at a time while i tweak my odor control. But would like to get some clones off my female plant and store them for future use.

In regards to this forum topic, would a 21W LED grow light keep them alive? (has blue and red spectrum combined)
Would my plants become too cumbersome to relocate if i left that light on them 20hrs/day for up to 4 or 5 months?

Mostly wondering the same as the original poster. What the minimum wattage is. I might be too low but im gonna try

The numbers I gave are for flowering, that is when a cannabis plant needs the most intense light, but plants can do with easily about half for veg, seedlings and clones need even less, especially if a light is extremely close, again – due to the inverse square law/property of electromagnetic radiation and the fact that lower watt lights can be brought much closer to the plants, lower wattage very close – can supply enough for seedlings or small clones.