Without a doubt, the 5000K bulbs. My favs are Daylight, which are in the 6,000-5,500K range. They produce much more blue spectrum.

Another "trick" is to keeps the temps as cool as you can, within reason of course. 55-60 degrees will produce short, stocky plants, provided you don't water with high N ferts. Tomato-tone is ideal for root growth and a $6 bag will last for hundreds of seedlings.

Mike

Thanks Mike. I didn't know if lumens outweighed spectrum. it sounds like it does not. I have used 6,500k daylight bulbs w/success in the past that put out 2,160 lumens (T12s). Short, stocky is what I go for. I don't need tall plants. Space is important to me. :)

Chris

Chris,

If you're only rearing seedlings and moving them outdoors after they reach a few inches, you should be fine with either bulb. If you were however growing them under lights to maturity, then the proper spectrum would be more important. You can always mix them as well... or shop at another store.

Rob