Our community garden plot is 20'x20' the garden also offers 10'x10' plots. They occasionally let someone have 2 20'x20' combined as a single plot for their use. The common area perimeter is jointly cared for and we have a bunch of grapes, fig trees and a few espalier apples. I know the city offers a raised bed options that are really tall, more than a typical raised bed that is like 4x8 and they reserve these for disabled gardeners. I view my community garden as a zone 2 / 3 space even though it is 15-minute walk from the house. It is an integral part of our overall approach to growing our own food. Community gardens rock, we do a ton of stuff on our own property, but we really enjoy being involved in the local garden with others.