size of room needed to grow?

Yeah, that's a great space for a grow - over 9 square feet. Number of plants is a huge variable and really just determines how soon you harvest. In your space you could grow just one humongous plant or, say, nine little ones - and a skilled, experienced grower could get the same yield in both cases. Obviously, growing one big plant takes longer than growing a bunch of smaller ones.

My advice would be to first decide how much pot you want from your harvest than work it backwards. Growers benchmark their grows by how many grams per watt were harvested. A competent grower can yield 1 gram per watt of lighting - the holy grail! Mere mortals like us are lucky to get .5 grams per watt. Note that the number of plants does not enter into the equation.

Let's say you wanted to end up with about a half a pound (say 200 grams). How could you do it? To achieve that goal (assuming you will yield .5 gram per watt) you would need 400 watts of lighting for your space. 400 watts is a little less than 50 watts per square foot of your space but still good. You now have your lighting requirement for your space. The number of plants is determined by how impatient you are. Growing nine plants to yield 200 grams will take less time than growing one plant, but one plant needs less resources (seeds, soil, nutes, etc.) than nine. And sometimes the number of plants plays into sentencing guidelines if you get caught. So it's a compromise (like everything in life) - one plant? four? nine? Only you can decide! Good luck bro!

 

So you're thinking of cfl's right? They would be good for your modest goals. HID's need a ballast and a hood and they cost more and you'll have to deal with the lots more heat they put out. For cfl's, 100 watts per plant is definitely a good guideline since cfl's have to be placed close to the plant - sort of draped around surrounding the plant. Have a look at Kamel's CFL sticky thread under 'General Indoor Growing'. You'd be good to go with 4 x 26 watt cfl's for each plant. GL!