We need a little more detail than how much light for 30 plants.
Are you growing them in a field or a 20'x20' room, or a 10'x10' room?
Are the going to be lollipops, or full bushes?
What medium are you growing them in?
What type of lighting are you looking for?
Is heat an issue?
Help us Help you. General rule of thumb is 50 lumen per sq foot min.
srry I was thinking abou hps and heat aint an problem im growing in 15 soil and 15 hydroponics meassuers i dont know now. thats the most i can come whit right now
The first few questions are really the most important. If you are growing them outside or in a greenhouse the requirements change greatly. Likewise, if you have 30 plants crammed into a 5x5 room you'll need less light to cover that area than you will if you are growing in a room where each plant has 5 sq feet of space (ie 150 sq feet). I would suggest at least 1 sq ft of space per plant at a bare minimum. Growing in two different mediums means that you are most likely not going to be doing a screen of green as the hydro tend to finish before the soil plants do.
20x20 Building would almost be required for a grow this size unless of course you have 5 mothers, 5 clones, 10 in veg, and 10 in flower. As you can see, the more information we have the better we can help you. Is the clone/mother room included in this? Are you vegging in another area first? How long are you vegging? All of these factors make a difference.
I have a 4x8ft tent that I started 20 plants and finished 12. The room was packed tight. I run two 600 watt and two 8-bulb T5's for a total of just under 2200 watts. My yield would likely have been higher with fewer plants. Had enough light but not enough space.
