I have a few lettuces growing in an old dishpan in a glassed-in porch.
The dishpan is about 9" x 14" x 4" and it has half a dozen small
mesclun-type lettuces in it. They grow about fast enough in short
winter days on a chilly porch for a small green salad for two every
week or two. I'd like to increase the production next winter by placing
a large, plastic-lined box on the patio table, aiming at about four
times the surface area and two or three generous salads a week. Does
anyone have any ideas on how deep my box must be? I'd like to minimize
the weight on the table but not make the box so shallow that it won't
grow healthy lettuce.

Kathy