Q.Where can I buy poles to grow pole lima beans
To use a straight pole, I know it must be between 6′ and 8′ tall, but how do you run the string so that the beans can run between the poles? I live in the Greensboro-Winston Salem, NC area.
For a straightforward set-up as you described, you would use strong twine tied between two poles. The string is zigzagged from the top and bottom to make a lattice for the vines.
Here are some visuals on how to string up pole beans, there are many clever ways to do so:
A tomato trellis, modified with vertical rungs of bamboo poles:
http://tallcloverfarm.com/1838/at-stake-pole-beans-need-your-support
A teepee trellis:
http://www.veggiegardener.com/how-to-build-teepee-trellis-for-pole-beans-garden-peas/
Here is a forum thread showing people's ingenuity in stringing up their pole beans:
http://www.permies.com/t/761/organic/Simple-trellis-green-beans
I hope that helps.
For more information on staking pole beans, please visit the following link:
https://www.gardeningknowhow.com/edible/vegetables/beans/pole-bean-supports.htm