I vote to start right now with about 1/4 t. per gallon of water. I've tried it with and without. The with works better for me. I use Botanicare Pro Grow at that stage. Think it about 3-5% N. I would have to go look to make sure. Now if you have some kinda nuted dirt I take this back of course. I like to add my own nutes and I dont use dirt.