meadow
Deeply Rooted
...and in a dark year, only the plants on the outermost edges will reach anywhere near full potential.4 inches between plants in the row, about 8 inches between rows. In a dry year, it is insanely productive. In a wet year, you're in trouble!
@jbosmith I followed the Square Foot Gardening model for beans I wanted to sample (no seed saving) with pretty much the spacing heirloomgal mentioned. Well, actually I did 4 inch spacing all around for smaller beans and 4 inch with 8 inch rows for larger beans. This worked well for green beans that bordered a major walkway. The dry beans on the interior of the bed (planted in 'block rows' that were 1 foot wide with 1 foot walkways in between) did okay, but I will be giving them more space next year.
Another drawback to what I did: as the bushes drop leaves there is too little air circulation and they are prone to mildew/mold like @heirloomgal mentioned.