Companion planting is the practice of planting two or more different plants together for mutual benefit. There are several factors to consider when selecting companion plants for an Ontario garden, including soil conditions, sunlight, and pest management. Here are some good Ontario garden companion plants:

Tomatoes and basil: Tomatoes and basil are a well-known companion planting pair. Basil repels pests like tomato hornworms and whiteflies, and its fragrant oils can help improve the flavour of tomatoes.

Beans and corn: In an Ontario garden, beans and corn make an excellent combination. The beans fix nitrogen in the soil, which aids corn growth. The corn acts as a natural trellis for the beans, reducing the need for extra support structures.

Cucumbers and dill are natural companions because they are members of the same family. Dill repels pests like aphids and spider mites, and cucumbers benefit from the shade it provides.

Carrots and onions: Carrots and onions make an excellent companion planting pair. Onions repel pests like carrot flies, and carrots benefit from the nutrients released as onions decompose.

Marigolds and peppers: Marigolds are known for their pest-repelling properties and make an excellent companion plant for peppers. Marigolds repel pests like aphids and whiteflies, which are common issues with pepper plants.

Lettuce and radishes make an excellent combination in an Ontario garden. Radishes break up the soil, making it easier for lettuce roots to grow. Lettuce provides shade for the radishes, keeping them cool and moist.

Squash and nasturtiums: Another excellent companion planting combination is squash and nasturtiums. Nasturtiums repel pests like squash bugs and cucumber beetles, and the flowers are edible, adding a peppery flavour to salads.

Beets and spinach: Beets and spinach go well together in an Ontario garden. Beets are voracious eaters who benefit from the nutrients released by spinach as it decomposes. Spinach also gives the beets shade, which helps to keep the soil cool and moist.

When selecting companion plants for your Ontario garden, keep in mind the specific requirements of each plant as well as the growing conditions in your garden. You can improve the health and productivity of your garden while reducing the need for synthetic fertilizers and pesticides by selecting the right plant combinations.