This is a science of compatible relationships, or as Alan Chadwick called, Relationships and Disrelationships. There are a lot of myths around companion planting and how it works. I would like to share what I do based on four decades of experiences that has been researched in different parts of the world. So this is an introduction that would be an entire workshop that takes a few hours. I utilize five components of compatibility. If I can incorporate more than one then the effects become multidimensional. First lets begin with physical or spatial. This is like putting together a puzzle. I fill up space efficiently so there is little room for weeds. This is how nature works. It creates a living mulch that protects the soil and protects the dynamic place where soil meets the atmosphere. Here are some examples. Use plants that do not compete for space. I plant a bed of leaf vegetables like lettuce, spinach in a staggered pattern. In between those plants I can plant a carrot, radish, turnip and fill the space very efficiently. I can also do this with large leaf crops like cabbage. They need to be planted almost a foot and a half apart in staggered plantings. I can plant fast growing turnips or dikon radish in between that open space. About the time the turnips or radish are mature is about the time the cabbage leaves begin to fill up that space. So this is a succession and two crops in one. Another example is to plant tall plants the serve as a trellis. Pole beans and corn are good for this. Along with winter squash, this is referred to as the three sisters. It is an old Native American example of companion planting. I grow cucumbers on a horizontal trellis. I plant a few sunflowers in between. The cucumbers climb onto to sunflowers nicely. The sunflowers attract lady bugs that clean aphids off of the cucumbers. A row of beans or peas planted on the west side of a bed can offer some afternoon shade for leafy greens. There are many more examples of doing this creatively. The next area is Biological. This involves using plants that will attract beneficial insects. This can also be referred to as organic IMP (Integrated Pest Management). I grow a lot of cut flowers for market and herbs. Many of them are host plants for beneficial insects. Umbelliferae, like Ammi majus, dill, cilantro, fennel, Queen Anne's lace are good for a wide range of wasps, damsel flies, lacewings, etc. The composite flowers like shasta daisy, sunflowers, and other daisies attract lady bugs, pirate bugs, predatory mites and so on. Allysum is wonderful for hover flies. Grasses attract spiders that eat most insects. Golden rod attracts soldier beetles. Yarrow attracts lacewings. One thing I often do is to plant borage around my tomatoes. The borage attracts the braconid wasp. The wasp stings and parasitizes tomato horn worm and plants it's eggs inside the worm.(photo below) This is a very effective way to curb their population. There is an extensive amount of flowers and herbs that provide a biological magnet for beneficial insects. Buckwheat attracts a wasp that gleam squash bugs. There are many examples of how this works.
The next area is Botanical. This involves plant pheromones that deter insects and diseases. Japanese beetles are attracted to delphiniums and larkspur. The beetles consume them and die. This is good around fruit trees. Tansy and mints are good around fruit trees susceptible to ant damage. Wormwood (artimesia) and catnip deter a wide range of insects. I plant garlic chives down in tomato beds. They do well with almost no sun. Many herbs are planted under plants that need to be trellised, like tomato, peppers and eggplant. This is an example of polyculture. Plants that produce essential oils are good to work with. The next is Chemical. This involves mostly root exudates. This is were plants give off oils underground that ward off insects and diseases. African black oats and French marigolds will get rid of root knot nematodes. Rosemary root exudates can inhibit many diseases, especially in tomatoes. Mustard oil discourages carrot wire worms. Garlic and many herbs are useful for exuding beneficial root exudates. The last section is nutritional. Legumes, like beans, peas, lupines, clover put nitrogen in the soil. A good rotation would be leaf crops. Dynamic accumulators concentrate nutrients and release them in the soil. Comfrey is excellent source of potassium, calcium, phosphorus, copper and iron. Plants can benefit from planting around it. You can also make a tea from comfrey to put on plants. Dandelion also accumulates potassium, phosphorus, calcium, copper and iron. Stinging nettle and lambs quarters accumulates Calcium, phosphorus, sulfur, iron and sodium. You can also turn these plants into the soil so they release nutrients as they break down. This is a highly experimental science. The results vary a lot from location to location and from year to year. There are many factors that determine the out come. like the weather. So it is not a matter of factual science. This is a system that involves diversity and diversity supports balance. There is more information in my book; Radical Regenerative Gardening and Farming.
