I'm interested in ideas like forest gardening, companion planting and intercropping. In a small way I experiment with them on the allotment. For example the Runner Beans are underplanted with Nasturtiums. The groundcovering Nasturtiums form a living mulch retaining moisture and suppressing weeds (and are an edible in their own right). The Runners climb above them.
 The next bed has three rows of Broad Beans, mostly Bunyard's Exhibition which is a tall variety (about 4 feet/1.2 metres). Once they got going I seeded the bed with Phacelia, the fast growing annual often used as a 'green manure'. It doesn't grow as tall as the Broad Beans so I speculated they might co-exist reasonably well. Then I noticed a lot of Borage had self-seeded from last year. I love Borage so I was loathe to weed it out. Broad Beans have a tendency to flop and there is a school of thought that says plant them close together to support each other. I hadn't done that but the thought occurred to me that the Borage growing among them might have the same effect.
 The combination of the three might work or it might not. Little experiments like this are what intrigues me about growing plants.