You want full-spectrum (daylight) incandescent flood light type bulbs. You should be able to find them at most hardware and big box stores. You can find them in 60, 75, 100 and 150 watts. I'd start with 100 watts.When you start using them, be sure to check the heat every couple of hours. That will impact how close to the plants you can move them. I think they probably cost around 7 to 10 dollars each... Be carefull how many you string on one outlet!!