I've been thinking of trying a cold frame for a number of years. I have:

1) south facing edge of garage, with no shade (~25 feet long)
2) about 13 2x4's
3) 5 or 6 double paned glass windows, roughly 3' by 3'

So I think I have what I would need to cobble together some sort of
test run, at little cost. I'm just trying to figure out if it could
work here in zone 6a, southwest Ohio.

One of my friends is paralyzed from the waist down and lives in an
assisted living community. I am in charge of shopping for his groceries
every week, including greens. Usually he has me buy spinach, though he
has tried kale and some other greens.

I'm wondering if there is any chance I might be able to supplement
his diet of greens by planting something in the cold frame.

If you think there might be a chance, I would really appreciate it if
anyone could suggest some varieties of greens that might be able to
handle the cold weather growing in a cold frame. I'm probably too late
for this fall, but might be able to plan for a late winter planting.

Thanks for your help!

Hello OhioGuy here are a few options for growing in a cold frame in winter. Arugula
Broccoli
Beets
Cabbage
Chard
Chinese cabbage
Green onion
Kale
Lettuce
Mustard
Radish
Spinach

I have only tried cabbage and mustard and they came up fine, the rest of the list I got from motherearthnews