Answer: I would reckon well less than a pound per 15 feet. Unfortunately, growing beans for drying takes a lot of garden space to get enough to do much with. Kidney beans are grown the same as any other kind of bean but can only be picked once, take a very long time to mature (about 100 days) and must be harvested dry or they will rot in storage. To grow them in a fifteen foot row would be sort of impractical -- but a fun project!
Q&A Library Searching Tips