I was pondering the connections between plants yesterday afternoon while snacking on a pesto and tomato sandwich. We’ve touched on companion plants in our Phytotheca, where each profile contains information about which plants you can keep as neighbors, as well as which need to stay apart!

Tomato and basil are a classic example of good neighbors. Why, you might ask? Well, the strong scent of the basil leaves is known to repel or confuse pests which might otherwise make a tasty snack out of the tomato plant’s leaves. Also, basil’s flowers attract pollinators which may also be beneficial in the garden in other ways, like eating pesty bugs. There are even rumors that the plants’ root systems interact in a way that makes them both more healthy and productive. Basically, everything is interconnected, and we don’t even always know how or why. But there is plenty of information out there for the gardener who is interested in companion planting.

Companion planting tips

There are a few ways that plants help each other out. First, like the basil above, a plant can either attract good bugs or repel bad bugs and other pests, which not only protects or benefits itself, but also does the same for its neighbors. Plants in the mint family, like basil, as well as mints, oregano, and marjoram, often fall in this category. So are many other strongly scented plants. Onions and garlic, and others in the Allium family, not only repel bad beetles, worms, and bugs, their strong smells can also keep hungry rabbits away. Flowers can also fit in here, like the marigold which repels microscopic nematodes in the soil while it’s alive, and continues to do so even after you till it into the soil at the end of its lifespan. Marigolds also attract beneficial bugs, which are brought into the garden by its brightly colored flowers. These pollinators may also find their way to your squash blossoms and tomato flowers, making sure that fruits and veggies form. Other bugs that are attracted to certain flowers might also like to prey on pesty bugs like aphids. Native plants are a great way to bring in good bugs as well.

Another way plants interact is that they provide shade for each other, or for each others’ roots. Large leaved or spreading herbs keep the soil cool and moist if they’re grown near to taller plants that need a moist or cool environment. Squash leaves are large and often grow low and close together, so they make a good soil shade for hot weather growing. Plants like ginger like a shady environment, which can be found under trees, so don’t leave your trees out when you’re considering a companion planting plan for your yard.

Plants can also support each other. In the three sisters planting method of corn, beans, and squash, corn stalks provide a trellis for the beans to wind their way up. Sunflowers are another good, tall, supportive plant that can become a trellis for climbing vines, as well as attracting pollinators.

Another thing that certain plants in the legume family do is that they take nitrogen from the air and move it into the soil, turning it into a form that is usable by other plants. This soil improvement happens because of a microbial relationship within the roots of these plants. This means that the Rhizobium bacteria that grows in nodes on the roots of the beans needs to be present. If your yard or soil is new to growing beans, you can buy an innoculant that you coat the bean or pea seeds in before planting them. This will ensure that your soil gets its share of nitrogen to be used by the next crop that comes along.

There’s also the idea of a “trap crop,” which is a sort of forfeit to the pests which hopefully keep enough of them occupied that your target crop maintains its health. One example is planting chervil in your garden to attract slugs to it, hopefully meaning they leave your basil and sweet peppers alone!

Read more about companion plants in your favorite gardening book, or talk to an experienced gardener in your life to see if they have any hints. And don’t forget to check the companion plants section in our plant profiles. We’ve got some helpful hints and gardening resources at our store, Culture Garden Market, as well. Happy garden planning!