The chemical compounds and defenses found in certain plants can have great benefits for other crops planted nearby. Certain crops can deter pests naturally, attract beneficial insects, add valuable nutrients to the soil, and provide shade and support for climbing plants.
Some favorite companion crop combinations of zone 5 gardeners are:
- Tomatoes: marigold and basil repel pests
- Potatoes: garlic, basil, oregano, beans
- The 3 sisters: corn, squash and beans
- Cucumbers: legumes, root vegetables, nasturtium, dill
- Carrots: onions repel the carrot fly, cilantro, oregano
- Lettuce: chives and onions repel aphids
However, there are also certain plant combinations that you will want to avoid planting near each other. In general, tomatoes and corn should not be planted near each other because diseases and pests can spread between them. Onions and garlic can hinder the growth of beans and peas. You may want to avoid planting mint, rosemary, and thyme near your other crops as they have a tendency to overgrow and outcompete nearby plants. It is also important to leave enough space between your companion crops so that they are not shading each other or competing for water or nutrients.
To get some more ideas for companion plants to grow in your garden, visit these links:
https://www.farmersalmanac.com/companion-planting-guide
https://www.almanac.com/companion-planting-guide-vegetables
https://www.grownyc.org/files/upload/gardens/companion_planting_by_cornell_co-op.pdf
https://www.burpee.com/blog/companion-planting-guide_article10888.html
For a comprehensive chart on plant relationships, click this link