Honestly, I don't think it makes that much difference. It all depends on what you want to spend. You can also find 4' "Grow-Lite" blue bulbs if you wish. I use the ones labeled Kitchen & Bath or Daylight and replace them annually. With 14 fixtures, that gets expensive. ;)

The lumen output and distance above the plants is what is important. Get the highest lumen output you can find and keep them no more than 1-3 inches above the plants.

The Growing Under Lights forum might have more info for you.

Dave

I agree with digdirt. I've tried various types over the years, and did buy the more expensive Grow bulbs last time. Can't really tell any difference. I went with the grow just in case there might be some benefit that I couldn't see.

Guess I'll try some of each since I need 8 bulbs to cover the trays. They're all about the same price (for standard T12's) at HD.

I would use the least expensive. It has been a few decades since I studied this but back then the more expensive tubes lost their effectiveness very quickly and were not much difference from the more expensive one. The grow lights, for example, had some wavelengths out on both ends of the visible range when new but back then they lost this advantage very quickly.

Depending on what kind of plants you're growing you might want to invest in a fan that can blow lightly over the seedlings when they emerge a bit (especially for herbaceous [non-woody] plants).

It keeps them from "bolting" up toward the lights while strengthening the main stem of the plant.

It helps later when hardening off and/or transplanting into a place where air movement is less predictable.

You don't need a special fan or any special equipment. Just a breeze light enough to put a little bit of movement (constant movement not necessary) on the plant that will trigger it to thicken up rather than putting all its energy into reaching for the sky.

Rick, As you've probably figured out the bulb industry is making major advances. I've had results all over the place with c.f.bulbs in my house use. As I said earlier, I couldn't see much difference between bulb types and only went with the grow lights to cover all bases. The most important fact is that all the bulbs work. Know this is not the answer you wanted, but after talking with many bulb manufactures, I'm not sure that they know either. Guess you'll have to join the research team. That's why I went with the grow lights...seemed more cutting edge...but if $ is a factor, I'd suggest the daylight. variety....honestly...they all seem to work. Enjoy watching the seeds sprout...I love that part of gardening.

It doesn't matter for seed starting.

If you wish to use artificial lights to grow a plant vegetatively then it matters.

If you wish to get a plant to mature and bloom/fruit under artificial lights then it matters.

For seed starting it does not matter.

Get some ballasts/fixtures and whatever bulbs are cheapest and whenever the weather is nice move the plants outside.

That is all that is necessary.

Oh, and keep the floros as close to the plants as possible and if you can point a fan at the plants to gently blow them around a bit to simulate natural breezes to strengthen the stems.