How much light does a seedling need indoors?
Ideally, marijuana seedlings need to receive a light input of 30 to 60 watts per square foot. Some growers start their seedlings under fluorescent light and then move them over to stronger lights. In my opinion, this tends to stress the cannabis plants. If provided inadequate light, seedlings tend to grow long, thin, unsupportive stems. If provided adequate light, the plants will grow sturdy stems that will support any further growth.