Asparagus, gooseberries, chives, garlic, onions, parsley, marigolds, nasturtiums and carrots are all good companion plants for tomatoes. Tomatoes protect against many pests, and for this reason, they are often planted with other vegetables that are particularly susceptible to pest damage. Plant tomatoes in the spring after the first harvest of asparagus to prevent the asparagus beetle from taking hold in a garden.
Planting tomatoes with gooseberries repels all natural pests from the gooseberry bush, while planting them next to garlic can help repel red spider mites, a pest of the tomato plant. Planting tomatoes near rose bushes can also prevent roses from developing the fungal infection black spot.
Tomato plants prefer to grow in the same place every year, making it important to have healthy soil free of disease. Stinging nettles and redroot pigweed can help to improve soil quality when planted near tomatoes.
Tomato plants repel all members of the Brassica family and therefore should not be planted alongside broccoli, cabbage, cauliflower or Brussels sprouts. Because the tomato fruitworm is the same as the corn earworm, tomatoes and corn should not be planted near each other. Do not plant tomatoes by kohlrabi or fennel, as these inhibit the growth of tomatoes. Avoid planting tomatoes by potatoes, as they can increase the potatoes' susceptibility to potato blight.