Companion Planting

The definition of companion planting has changed over the years. In the past, it meant planting specific plants, “companions”, with your plants to deter pests. Now the definition leans towards planting specific plants with each other for many beneficial results. It needs to be stressed that no plant can completely repel pests or problems. Most companion plants either attract beneficial pollinators and predators or they disguise the scent of our plants.

Heavily scented plants attract butterflies, which along with bees, flies, beetles, and spiders, help pollinate our plants. Evening scented plants attract moths and fireflies which also pollinate our plants. Scent not only attracts pollinators, it also attracts predators.

Sweet Alyssum (Lobularia maritima) is a heavily scented annual that smells like honey and attracts aphid predators. If it is planted in and around your garden, you will find less aphid damage.

French marigolds (Tagetes patula) are the most heavily scented of the marigolds and are often planted in pots of flowers and vegetables because their scent is off-putting to squirrels, chipmunks, and rabbits. The marigold also attracts predators such as a tiny parasitic wasp that protects our plants by killing the pests that damage them. 

Planting radishes (Raphanus sativus) with pumpkins, squash and cucumbers is a very old technique for disguising the scent of these plants. The pests often associated with these vegetables rely a great deal on scent. For the ultimate radish scent, I have used the black Spanish radish. It is amazingly large, very hot to eat and its scent is extremely strong.

Dill (Anethum graveolens) is a wonderful plant to grow. It works deliciously in a tuna salad sandwich while being indispensable in pickles. If you plant dill around plants in the cabbage family including broccoli and Brussels sprouts you will find that they attract tiny parasitic wasps primarily those within the Braconidae and Trichogramma families that will help to take care of those cabbage worms. I plant about twice the amount of dill that I need because it also feeds the caterpillar of the swallowtail butterfly. I am more than willing to sacrifice some of my dill for those butterflies.

Catnip (Nepeta cataria) is another plant that can be used as a companion. Catnip has a very strong scent and seems to be a plant that rodents find offputting. Catnip often attracts flea beetles and can be used as a trap crop to keep beetles away from your vegetables. It can also be planted with the cabbage family to attract parasitic wasps. However, catnip is attractive to cats so be careful where you plant it in case you begin to get furry visitors. I dry my catnip for my cats which they truly appreciate.

Calendulas (Calendula officinalis) are beautiful, highly colourful annuals to plant around your garden. They are edible and you can make an oil or cream from their flowers. Planting them around cucumbers and zucchini means that you will attract pollinators at times when there seem to be very few around.

Nasturtiums (Tropaeolum) are a wonderful companion. They attract hoverflies that prey on aphids and can be used as a trap crop for nasty pests. In addition, with their very sweet nectar and funneltype shape, nasturtiums are very attractive to hummingbirds. Their peppery leaves and beautiful flowers are quite delicious in a salad or on a sandwich. They germinate quickly from a large seed and are ideal for a child’s garden.

Here’s a little how-to lesson to illustrate the usefulness of companion planting. You can use the same directions to plant in the ground as you would for planting in a pot.

If you are planting your tomato in a pot, choose as large a pot as you can find. Plant the tomato nice and deep and then surround it with companions. Plant sweet alyssum to attract aphid predators and allow the alyssum to spread and form a living mulch. Tomatoes need mulching so that the rain doesn’t splash up on their leaves and cause early blight. I cover the surface of the soil around my tomato with straw until the alyssum has had a chance to spread. Plant French marigolds as they have a stronger scent, and they attract a parasitic wasp that protects your plants. Plant basil too as it has been shown that basil attracts bumblebees and bumblebees are the best pollinators for your tomatoes. Adding a few radishes means that you reduce the threat of flea beetles which prefer radish leaves to anything else. 

As well I like to add borage; it is such a magnet for pollinators. With these plants all gathered together you will end up with your own little ecosystem.

In 1983, Roses Love Garlic: Companion Planting and Other Secrets of Flowers by Louise Riotte, was published. While many seasoned gardeners and farmers had long-running tried and true methods of using companion planting, this book popularized the idea of plants helping plants. Unfortunately, this also seemed to bring forward the idea that if you plant a certain plant, you will no longer need to worry about pests, disease, and weeds. Such a plant does not exist as far as I have found. So let’s turn that definition on its head and view companions as select, specific plants that attract beneficial pollinators and predators.

Planting garlic along with other alliums can be beneficial for your roses and perennials. The strong scent of alliums helps to disguise the scent of tender perennials (making it harder for pests to find them) allowing them to grow. There are beautiful alliums you can plant as a bulb in the fall around your perennials and roses; these will grow and bloom early giving colour and scent to your perennial garden. The allium flowers attract pollinators and aphid predators such as ladybugs. The perennials and other plants in your garden will be growing well as the alliums finish their blooms.

Remember, there are no magic plants. Nothing prevents weeds or repels every pest. There are plants however that will greatly benefit your perennials and vegetables, either by disguising the scent or by attracting pollinators and predators.