Habitat, the trellis I use is 7.5' T-posts driven into the ground, with rebar top & bottom supports, and string run both vertically & horizontally. The top rod is run through 1.25" PVC T's placed over the top of the posts. This results in a trellis just over 6' tall (and easily reachable) with a string lattice with about 12" squares.
Most of the pole beans will reach the top. For the most vigorous varieties, I allow the main runner(s) to reach 2-3 feet beyond the top, then train them further down. Branches, and varieties with less vigorous runners, I just leave to themselves (except for limas). This results in some bunching up at the top late in the season, but provided the plants are widely spaced, this is seldom a problem. If the top growth becomes excessive, I trim some of the main runners.
The problem with very tall supports isn't only that they are hard to pick from. They also cast a longer shadow. This is not an issue if the trellis/support is on the North side of the garden; but if it is placed elsewhere, or if there will be multiple trellises, then large areas of the garden will be in full or partial shade. When I grow multiple rows of a pole bean with the 6' trellis design, the rows need to be spaced at least 42" apart to prevent shading which would otherwise reduce the yield of the inner rows. I try to run such multiple rows in an East-West direction.
Not sure where you are located, Habitat, but for much of the 80's & 90's, I lived and gardened in San Diego (where I had a source of unlimited free manure) & San Jose (where I gardened on a fertile flood plain). Those were some great gardening years, you could grow almost anything there; I really miss it. Wish I had known about the Seed Savers Exchange then, I would have really had fun!
|