Alot depends on the size of the plant.

I had 30 two foot mothers under a 400 watt hanging straight down with a parobolic hood and it was fine. If you track a 600 watt and rotate your plants you can cover a 5 foot by 7 foot area no problem.
Sparrow Reviewed by Sparrow on . How many plants under a 600w HPS? Hi, as you all know I have a 600w HPS in a cabinet lined with mylar. Im just wondering how many Lowryders Ill be able to grow under there. By the way, I can fit 6 in, but depending how well they do in the small pots Id be able to fit 8 in. Rating: 5