I have a passive solar attached greenhouse in which I grow chard, kale, tatsoi and lettuce through the winter. Growth rates are slowing dramatically as the light lessens and I'd like to try supplementing with grow lights. I'd like to do this cheaply, and I have some fixtures for tube lights.

From what I've read online I think I should be using fluorescents. I'd be interested in hearing your thoughts on cool white vs. wide/full-spectrum. I'm also trying to figure out spacing. I've read articles recommending keeping the lights as close as 4 inches from the plant tops, but then it seems that the light wouldn't spread at all well to the plants on either side. I'm growing some plants in 1x2x3 boxes, should I be able to use just one two-bulb fixture per box? Finally, how many hours of light/day do kale, chard etc want?I've read that lettuce prefers 10-12.

Any advice would be much appreciated.

Joanna