8x8 shed and 2 400w lights?

wrong section man, you'll get more help if you scroll a little further down the forum.


edit: i just read your post, and i don't know to much about inside growing but no, you cannot spontaneously flower a plant thats only been vegging for 3 weeks.

 

Two 400 watt lights will work but it's less than ideal for that space. Paint the inside of the shed flat white or cover the walls with mylar to help reflect some light back to your plants. One ounce per plant sounds reasonable under normal circumstances but you have a bigger problem. You absolutely can go to flower with 3 week old plants, but you will be severely overcrowded with 12 plants in that space if most of them turn out to be female. They're going to stretch to 2 or 3 times their current height and fill out considerably when you go to 12/12. While the footprint of your shed can probably accomodate 8 plants, you won't have any room to move around inside and tend to them. It will be plants wall to wall.

 

Are you growing from clones or from seed where you'll be culling some male plants?

 

no worries, it might just get moved by a mod.

if you grow 8 plants it is possible that they will grow better than if you used 12. Mainly being because each plant will receive more light. However, 3 weeks is way to short.

 

Why do you say 3 weeks is too short? Lots of indoor growers go 12/12 right from seed to limit height. I usually go to flower at 4 weeks. It limits yield but produces the same quality of bud. You have to make adjustments when you grow in confined spaces.

 

I'd still go with the 2 600's if possible but you should easily be able to do an ounce per plant with the two 400's if you're realistic about how many plants you can fit. Try 8 or 9 plants clustered as close to the center as possible. Try to to keep a small path around three sides so you can travel around the room. Center the lights over the plants, not the room. Get through this grow but research topping and training techniques to maximize yield for your next grows. Expect between 2 and 3 ounces per plant when you get the hang of it.