Answer: Unfortunately, corn requires a large amount of space. It should also be planted in blocks of at least four short rows rather than all one long row to assure good pollination, so the 18 foot long space you have is not too suitable to corn unless you plant to hand pollinate it. In general it is a good idea to plant varieties that do not mature at the same time in order to avoid the cross pollination problem. This is generally only a serious problem, though, if you are growing a normal corn along with a super-sweet corn at the same time. Ideally you would probably separate your varieties by at least 25 to 50 feet, although for true purity you would need to separate them by over a thousand feet.
Bush beans can be planted in a matted row and spaced about four inches apart, or can be grown in a normal row spaced about an inch apart with the rows at least a foot apart. They are good for filling in gaps in the garden and can be planted every few weeks to assure an ongoing supply.
Pole beans require trellising and take longer to come into production but also stay in production for a long time. They require more room depending on the design of your support or trellis, and can be planted about an inch apart along the fence line.
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