The natural extension of the organic principles of diversity and coexistence is to figure which plants can spend their entire time together — that is, can be “interplanted.” This is largely a matter looking at the growth habits of the plants in question—both above and below ground—to see if they are complementary rather than in competition with each other.
One of my favorite interplanting schemes is to plant a quick crop of spinach between the pea rows. I put a row of spinach on each side of the pea fence, which runs down the center of a three-foot-wide bed. This way, the space does not go to waste while the pea vines are just getting going, yet the spinach is long gone before the peas need the room. This same principle applies to many other crops. Whenever you have a tall crop like peas, pole beans, corn, or trellised cucumbers, you can find a crop that will thrive at its base without competing. In fact, the shade created by a tall crop may well provide the best place in the garden for shade-tolerant but heat-sensitive summer greens.
Another favorite strategy of mine is to set young basil and marigold plants on the edge of the tomato bed, alternating with the tomatoes. This particular combination of plants—and a whole range of others—are thought by many gardeners to have a positive effect in pest and disease control. This body of lore, known as companion planting, deals with the mutually beneficial (or detrimental) effects different plants growing in close proximity will have on one another. Basil and marigolds may well improve the flavor of the tomatoes and repel insects; but the simple beauty of the arrangement, and the convenience of having the basil and tomatoes near each other at harvest time, is reason enough for me to interplant them.
Tradition also has it that planting herbs like Sage among the broccoli will repel the cabbage butterfly, but in my garden, where herbs do alternate with the broccoli, I certainly haven’t noticed any effect. In fact, I’ve caught the butterflies mating on the sage and the dill plants. However, I do get a “free” crop of herbs from the bed that was prepared for the broccoli. So whatever the reason, be it beauty, productivity, or even pest control, interplanting is a practice worth pursuing.
In fact, all three of the techniques we’ve discussed here—rotation, succession planting, and interplanting—are excellent examples of ways in which an understanding of the plants, the soil, and the seasons can lead to big gains, regardless of the size of your garden. And planning can be fun: it’s great, cheap entertainment for those long winter nights when garden dreams are the only green we’ve got, and it’s educational at the same time. A garden is like a huge jigsaw puzzle that exists both in space and in time, and trying to figure out better ways to put all the pieces together can be a fascinating and stimulating pastime.