The closest that I have come to this is growing the half-runner Bert Goodwin in a self watering container in a greenhouse. The soil was about 6-7 inches deep. The vines grew to about 5 feet, longer and earlier than outdoors. - Dick

The only beans I've grown in one gallon pots in the greenhouse were two little rice beans. One plant per pot, they actually did quite well. I wanted to compare the differences between the two varieties.
I grew Comtesse de Chambord in hanging baskets with pretty good results, this year I'm going to plant a row of them in a raised bed.
I've also grown a few bush varieties in 5 gal tubs, just to see what they're like. All beans grown in containers have been in Sunshine Mix #4.

Annette

Most gallon pots(nursery gallon)are 3 quarts.
I would use gallon milk jugs or 2 gallon pots(6 quarts or so).

Ran across this, it may be helpful?

http://www.extension.iastate.edu/publications/pm870b.pdf

Here is a link that might be useful: container vegetable gardening

Well, I think it would work at one or possibly two plants per pot, but they're going to dry out fast and take a lot of attention. Honestly, I think you'd be much better off in much larger containers, so you aren't out there watering twice a day. Just my $0.02 worth.

Thanks so much for the responses. I planted the beans after Annette talked about her Comtesse de Chambords in pots. I think it's funny how we call those pots gallon pots, but they really aren't. Also, it's still cold, and the sun isn't shining too much, so the pots haven't dried out. The greenhouse also keeps it humid, which might be keeping the soil moist. I will probably be watering a lot when the sun is out longer.

I don't have a greenhouse but I've grown bush beans (Dragon Tongue--my favorite) in a 5 gallon bucket outside my garage. I put 7 in one pot, I think, with a couple of well-branched twigs inserted for support. They grew like mad, and I got lots of beans, right up until the frost. It sounds crowded, but you can grow 9 bush bean plants per square foot, if you use the square foot method.

Update: I've got flowers! I planted six of the Thibodeau de Comte bean plants in the "gallon" pots around the 25th of February, and the plants are about 10 inches tall. I'm pretty sure thy are stunted, I feel like they would grow more in the ground. Anyways, The flowers are just about to bloom, and I should have beans within the 45 days that Heritage Harvest said the beans would produce in.

Last summer I stuck some wax bean seeds into one of those half wine barrel planters and they did great- they were at most 18" high. There were maybe 6 seeds in there? We ate wax beans for weeks.