Written by Angus Stewart
Companion planting involves growing one plant next to another in order to provide beneﬁcial effects for one or both plants, such as repelling pests, ﬁxing nutrients in the soil, or simply providing shade for other plants.
Companion planting cannot be relied on to solve major garden problems or pest infestations, rather it is a lot like preventative health for your plants because it provides subtle beneﬁts for the whole system. Even just the simple act of interspersing the vegetable bed with herbs or other species helps to break up the monoculture and make the whole patch less susceptible to a major pest or disease outbreak.
Some of the main functions of companion plants are:
• controlling pests (either repelling unwanted insects or attracting beneﬁcial insects)
• attracting pollinators
• ﬁxing nitrogen in the soil (legumes)
• providing shelter, shade or support for other plants
• enhancing the ﬂavour of nearby plants
Companion planting is not a rapid solution to problems in the garden. It can take at least one season for the plant to start affecting the cycles in the garden, so it is best approached as a long-term and preventative strategy, to be used in combination with other organic gardening strategies. It is also quite an experimental science, so it is important to try different combinations of plants and be open to varying results. Factors such as the density and ratio of plantings can affect how successful companion planting is, so if you feel it’s not working, play around with different combinations to see how the various factors are affecting the outcome.
Some companion planting combinations have been developed over long periods of time, such as the pairing of beans and corn practiced by First Nations people in North America. This partnership is a great example of companion planting, showing multiple beneﬁts to each plant. The beans ﬁx nitrogen in the soil, making more nutrients available for the corn plants, while the tall corn plants provide a climbing frame for the beans. This can also be replicated with other legumes and vegetables, such as growing peas and beans with kale and lettuce. The leafy greens use up a lot of nitrogen from the soil, so growing the legumes with them will help to replenish that and keep them thriving without any outside input.
Growing decoy or ‘sacriﬁcial’ plants can help to divert pests from your vegetables, as they attack the decoy plant instead. Nasturtiums are a great choice for this.
Another useful decoy plant is marigold (Calendula ofﬁcinalis) which can be planted near crops of leafy greens to attract slugs and snails away from them and into the marigold plant. Nasturtium also deters aphids, as do plants in the Allium family, like garlic and chives. Plant garlic near roses and raspberries to keep aphids away.
To attract beneﬁcial insects, plant herbs like borage and dill. Dill attracts a type of wasp which helps to control cabbage white butterﬂy, and so it can be planted near Brassica species such as broccoli and cabbage. Borage attracts all kinds of pollinators, as do other herbs, so planting these throughout the garden or close to plants like strawberries and tomatoes can help to improve their yield by improving the pollination rates. Other herbs such as lemon balm, sage, basil, and mint are also great for this purpose.
Now that you have the background information, here are a few combinations to try:
• Corn + climbing beans
• Leafy greens (kale, lettuce) + legumes (peas, beans) + marigold (Calendula ofﬁcinalis) around edges of bed
• Strawberries + borage/lemon balm/mint
• Tomatoes + borage/lemon balm/mint
• Roses/raspberries + garlic/nasturtium
• Brassicas (cabbage, broccoli, kale) + dill