Per Nancy Bubels "The New Seed-Starters Handbook" Mix a cool white and warm white in 1 fixture. Cool white bulb 1.59 Warm white bulb 1.79 Grow bulb 8.99 Tried it last year, plants were a little yellow, one day in sun took care of that Suggest using 48 in lights, reason bulbs are easier to get and cost less. Byron A continuous student of gardening