If they are over 8" they can go straight in at 24/0 -12/12 If they are smaller or even seedlings, keep them to one side and 3 feet away 18/6-24/0You should harden off the plants under the hps. Put them under it for 1 hr the first day, 2 the second, and so on, for about a week before leaving them under it permintly. You could shock the plant just putting it in there. Expecialy seedligs.