Proponents will spend hours figuring out the juxtaposition of plants in their garden, to gain the best growing advantages and most insects control. Those who poo-poo companion planting say there are no studies to verify it. Well, studies follow the money and there’s not much money to be made in verifying home remedies. Plus, companion planting is more of a home gardener technique than something done in commercial fields. It would be very hard to study the efficacy of companion planting when every garden is different, every season is different, and sometime different spots in the yard are different.
So the bottom line is that companion planting comes with no guarantees. Plant your basil near your tomatoes for convenience, but don’t expect a noticeable flavor difference.
However there are two areas of companion planting that deserve some consideration from home gardeners: deterring insect pests and attracting beneficial insects.
Using Companion Plants to Deter Pests
Nothing is going to keep hungry insects away 100%, but you can make your vegetables less tempting to pests cruising by for a quick snack. Usually it’s the scent of the companion plant that keeps pests away. If you’re hungry for cabbage and you get a whiff of mint, it’s not going to lure you to land.
Sometimes the companion doesn’t really deter the pest so much as it lures it away. Aphids love nasturtiums and will flock to them, rather than suck on a tomato. The nasturtiums are used as a sacrifice crop.
|Aphids||Chives, Coriander, Nasturtium|
|Bean Beetle||Marigold, Nasturtium, Rosemary|
|Cabbage Moth||Hyssop, Mint, Oregano, Rosemary, Sage, Southernwood, Tansy, Thyme|
|Carrot Fly||Rosemary, Sage|
|Flea Beetle||Catmint,, Mint|
|Fruit Tree Moths||Southernwood|
|Japanese Beetles||Garlic, Rue, Tansy|
|Squash Bugs and Beetles||Nasturtium, Tansy|
|Tomato Horn Worm||Borage, Calendula|
How Beneficial Insects Benefit Your Garden
Beneficial insects are considered good garden companions because they don’t munch on your plants, they munch on the other insects eating your plants.
❦ Parasitoid wasps – feed on aphids, caterpillars and grubs
❦ Lacewing larvae – feed on aphids
❦ Ladybug larvae – feed on aphids
❦ Ground beetles – feed on ground-dwelling pests.
❦ Hover flies, and Robber flies – feed on many insects, including leafhoppers and caterpillars
Sometimes they do this in their larval stage, when they are extremely hungry and sometimes they don’t really become beneficial until they are adults. That’s why it’s important to welcome them in your garden no matter what stage of development they’re in.
To attract them to your garden – and keep them there – there has to be something for them to eat. So don’t reach for the spray can every time you spot and aphid. That ugly little creature at the top of this page is a ladybug nymph and she can eat a whole lot of aphids before she becomes the familiar spotted lady beetle.
They also need host plants to lay their eggs on and for the larvae to feed on, as well as shelter. This extends well beyond the growing season. Ideally you should leave some plants standing, to give these “good” insects somewhere to over-winter. Hedgerows are great for this, but nearby trees and shrubs will do. They tend to leaf out in the spring earlier than we plant our vegetable gardens, providing shelter and a food source.
In the garden itself, herbs are a great way to make beneficial insects at home. They do double duty, since the insects don’t actually harm the herbs and you can still harvest them as needed.
Ways to Invite Beneficial Insects to Your Garden
❦ Tiny flowers and flattened flower heads of the Umbelliferae family (angelica, clover, coriander, dill, fennel, rue, yarrow)
❦ Flowers from the daisy family, like chamomile, and mints to attract hover flies, predatory wasps, and robber flies.
There is no hard science behind companion planting, but we do know that diversity in the garden is a great way to cut back on problems in general, so why not put some of this folk wisdom to the test and see if it helps.