There are a few reasons why I wanted to write a little bit about companion planting. One of them is that this concept is a perfect example of what Permaculture is all about. We use the term “plant guilds” to describe the groups of plants that like to grow in each others vicinity. One of the best-known guilds includes tomatoes and basil, lesser known members of this guild would be asparagus and sweet pepper.
The benefits derived from placing complementary plants together can be due to a number of reasons. Sometimes one plant would attract insects that are a natural predator of an insect that tends to be a pest to it’s companion plant. Marigold and Petunia are commonly used to attract pest-predators into an eco-system. Another way in which neighbouring plants can benefit each other is through the sharing and exchanging of minerals and nutrients through their roots. Legumes [peas, beans] can “fix” nitrogen in the soil by accumulating it in their root nodules from the atmosphere. This nitrogen is then available for neighbouring root systems to take up if needed. That is why it is common practice to follow Legumes with a nitrogen-hungry family in the crop rotation system.
There is a physical dimension to companion planting too. One good example of this is “The Three Sisters” a plant guild developed by the South American Incans and still used today on the slopes of the Andes. The three sisters are Pumpkins, Corn and Climbing Beans. They demonstrate another very important concept of permaculture, and remind us that the principles of permaculture are not always new, but coincide with ancient wisdom. This principle is referred to as “stacking” in permaculture, and can be applied in many other situations. In this particular stacked system, the pumpkin vines spread across the ground, finding gaps between it’s sisters to capture light with it’s impressive leaves. The corn shoots upward, utilizing light in the vertical plane, and the beans use the sturdy corn as a climbing frame. The result of this combination is three crops from one field, little or no weeds because the pumpkin covers the ground, and the nitrogen fixed in the soil by the beans is available to the the other two hungry companions.
The difficult part of companion planting is to remember which plants go together and to try integrating this knowledge into a planting plan. There are some useful guides available in books and on-line, but it is tricky to collate so much information into one document, table or chart.
I have also come across an excellent spreadsheet version, compiled by Ute Bohnsack and kindly made available to the anyone who follows this link..
You might have noticed that some plants in the above chart are a good companion with almost every other plant. Yarrow, Tagetes and Petunia in particular. These plants wouldn’t be considered in a conventional allotment planting plan, but perhaps they should be, especially considering Yarrow is a valuable medicinal plant, Tagetes and Petunias are edible and they also add some colour to the picture. Pot marigold [Calendula officinalis] are a popular companion due to their popularity with pest predators [the hover-fly in particular, a natural predator of aphids] and their medicinal potency.. they are also quite tasty!
Of course it is possible to experiment in your own garden and observe what plants like to grow together. Please let me know if you come across any winning combinations.
Thanks and respect to the creators of the useful guides above.