The basic idea is to have a balance of Red and Blue light.

The 'cool white' tubes are bluish, especially seen side-by-side with 'warm white' tubes. Which by comparison themselves look pinkish.

You can start seedlings under 'warm white' tubes but they might be a bit confused by it.

On the other hand, lots of people start seedlings under cool white alone.

Seedlings will grow fine under just a warm white, at least for a while until they are ready to go outside. If you can get a cool white then that has a slightly better balance of light for plants. There are also bulbs labelled daylight, which are generally even a little better. Next up the price ladder are special funny coloured lights just for plants.

I would suggest that you don't spend loads of money on a bulb until you have a really really good idea of what you might be getting. Stick with the warm whites for now, and cool whites if you can get them.

I am probably better off just buying grow lights instead. I bought the flourescent warm ones where there is very little selection. I will head to HD to get better ones. Probably be better in the end, right??!!

HD mostly carries CFL lights in the strongest wattage(42W) in a warm coloration. I've never seen any bulbs about 13W or 26W in cool or daylight color. I use them, just the same, and everything grows anf flowers for me. YMMV.

Sam

Was in HD today and got 10 cool white 20watt T12's for $3.49. My fixtures only hold 24 inch. Thought that was a good deal. Jane

Sam, the box stores tend to carry only the soft/warm white CFL bulbs for domestic use in typical 11W-20W powers. CFL bulbs do exist in all colour temperatures and a wide range of powers, but you might have to mail order. Don't be tempted to pay silly money, there are companies out there selling $5 6500K bulbs for $20 as special daylight bulbs for your health. 6500K bulbs with CRI above 80 tend to cost a few cents more and bulbs with CRI above 90 for colour-sensitive tasks can be quite expensive.

I know this, I wqas just relating my experiences with hardware stores such as HD. I generally order from ABCBulbs.com or Topbulbs.com, always in 6500K, alwqays stronger thqan 42W.

THat having been said, 42W bulbs are almost bright enough for one or two plants, and the coloration in a "warm" color doesn't seem to make a difference to the plants.

Sam