Tomatoes are notorious for their demanding and sensitive natures.
Anything from changes in nutrient level, temperature, sunlight, moisture, wind, air, disease, spacing, and pests can affect tomato yields and quality.
This sensitivity means they may be affected by various problems, including tomato rot, uneven ripening, curling leaves, and blossom drop.
However, planting tomato companion plants may prevent many of these and other tomato problems.
Below, we’ll go over what companion planting is, as well as provide a list of the best and worst companion crops for tomatoes.
What is companion planting?
Companion planting, also known as intercropping for small-scale gardeners, is the practice of growing one or more crops near one another to benefit one or both.
Some crops, when planted together, share at least one of the following beneficial qualities with their companions:
- repelling insects
- attracting pollinators
- enhancing soil nutrients
- suppressing weeds
- providing shading
- keeping moisture in
- providing natural structural support, etc.
However, some companion plants may directly compete with or even harm their companion crops.
Below, we’ll go over the best and worst tomato companion crops.
The Best Companion Plants with Tomatoes
A common adage among chefs and wine enthusiasts is, “what grows together, goes together.”
The below plants make excellent tomato companion plants (and also happen to go well with tomatoes when eaten):
- Basil. Tomato and basil are a match made in heaven in a bowl of soup. Basil is also one of the best companion crops for tomatoes in the garden, helping to ward off tomato pests like mites, mosquitoes, aphids, and tomato hornworms.
One study shows that tomatoes planted with basil saw increases in certain amino acids, sugars, and lycopene – all of which contribute to better aroma, growth, color, nutrient uptake (such as nitrogen), root development, and taste in tomatoes. [1]
- Other herbs in the Lamiaceae or mint family (e.g., mint, rosemary, sage, thyme, hyssop, lavender, perilla, spearmint, catnip, lemon balm, bee balm, and oregano) also help repel pests and attract pollinators such as bees.
Essential oils found in oregano, for example, repel the Silverleaf whitefly that often feasts on tomatoes. [2]
Spearmint repels ants and helps keep aphids, vectors for many tomato diseases, away.
- Legumes (e.g., peas, beans, peanuts, clovers, and lentils) are nitrogen-fixing and improve organic soil matter. They make great companion plants for most hungry vegetables, such as tomatoes.
- Alliums (e.g., chives, onions, leeks, and garlic) have a strong odor and chemicals that ward off pests. Garlic, for example, protects against red spider mites and helps control late blight on tomatoes and potatoes. Alliums, however, inhibit peas and beans, so choose one or the other with tomatoes.
- Root vegetables such as carrots, radishes, shallot, and beets help loosen the soil and improve nutrient and water uptake in tomato plants. Tomatoes also provide some needed shading for carrots in hot summers.
- Parsley, celery, coriander, and cilantro thrive under tomato shading and attract beneficial thrips and aphids-feeding predators. Coriander and parsley also repel harmful insects such as spider mites, aphids, and beetles.
- Lettuce and spinach both go well with tomatoes in salads and also provide ground cover, keeping weeds at bay. Tomatoes also help provide shading to these plants.
- Asparagus. A chemical found in asparagus juice is effective in the killing of nematodes, which can plague tomatoes. Tomatoes protect asparagus against asparagus beetles due to a substance called solanine found in tomatoes.
Other popular flowers and plants that go well with tomatoes include the following:
- Nasturtiums deter white flies, attract beneficial bees and hoverflies, and keep fungal infections at bay. However, they also attract aphids and squash bugs, so plant them at a small distance from tomatoes to distract these pests from your tomatoes.
- Marigolds. These flowers help deter nematodes, slugs, tomato worms, fruit borers, and other pests.
- Parsley helps boost tomato nutrients and growth and attracts beneficial insects, which eat tomato hornworms. However, they shouldn’t be planted near mints or alliums, as they will stunt each other’s growth.
- Roses go well with tomatoes and parsley. Parsley helps boost the fragrance in roses, and tomatoes protect roses against black spots.
Solanine, a volatile alkaloid found in tomatoes, was once used as an agricultural insecticide. Blend tomato leaves with water and a tablespoon of cornstarch to make a natural spray against Rose black spots. [3]
- Sunflowers attract bees, which help pollinate tomatoes. They also attract aphids away from tomatoes. Large sunflower stalks also provide trellis support for smaller vining tomatoes.
- Gooseberries. Tomatoes and gooseberries have similar water and growing requirements. Tomatoes also protect gooseberries from pests such as the gooseberry sawfly.
- Borage attracts pollinators such as bees and other aphid predators. They also deter tomato hornworms.
- Cowpeas attract southern green stink bugs, which also feast on tomatoes. Plant them away from tomatoes to keep pests distracted.
- Squash, cucumber, or zucchini provide excellent ground cover for tomatoes, suppressing weeds. These plants also thrive in similar conditions as tomatoes.
- Nettles. Although sometimes viewed as weeds, stinging nettles improve the potency of herbs, enrich compost, and attract beneficial insects. They also contain chemicals that help tomatoes keep longer after being picked. [4]
- Oats, winter rye, and sweet potatoes make excellent ground covers for tomatoes, suppressing weeds. They also help prevent splash-up from rain, which spreads fungal diseases. Oats also make great organic mulches for tomatoes after decomposing and dying through the winter.
The Worst Tomato Plants Companion
Other plants, however, make lousy companion plants for tomatoes and should be avoided:
- Strawberries attract similar pests and diseases to tomatoes, such as verticillium wilt. Pests that love feasting on strawberries will also eat tomatoes.
- Other nightshades such as potatoes, eggplant, and peppers belong to the same family as tomatoes. These plants are all susceptible to blight and attract similar pests like hornworms. They also compete directly with tomatoes for nutrients.
- Brassicas (e.g., cabbage, broccoli, kale, collard greens, kohlrabi, cauliflower, etc.) compete with tomatoes for nutrients, causing stunted growth.
- Corn. Tomato fruit worms and corn earworms are identical species, so planting corn will invite pests that also affect tomatoes. Corn grows quite tall, competing with tomatoes for sunlight and nutrients.
- Fennel is a bad companion for most garden crops as they release anti-growth compounds in the root zones.
- Apricots. Tomato root excretions have an inhibiting effect on apricot trees. They also transfer fungal diseases, which may kill the apricot trees.
- Walnuts produce a chemical called juglone, which is toxic to tomatoes. Grow tomatoes at least 50 feet away from walnut trees, or avoid them entirely.
- Dill. While tomatoes benefit from many herbs, including young dill, mature dill releases chemicals that negatively affect tomato roots, stunting growth.
References:
[1] Ahmad, H., Kobayashi, M., & Matsubara, Y. I. (2020). Changes in Secondary Metabolites and Free Amino Acid Content in Tomato with Lamiaceae Herbs Companion Planting. American Journal of Plant Sciences, 11(12), 1878–1889. https://doi.org/10.4236/ajps.2020.1112134.
[2] Pouët, C., Deletre, E., & Rhino, B. (2021). Repellency of Wild Oregano Plant Volatiles, Plectranthus Amboinicus, and Their Essential Oils to the Silverleaf Whitefly, Bemisia Tabaci, on Tomato. Neotropical Entomology, 51(1), 133–142. https://doi.org/10.1007/s13744-021-00921-y
[3] Unknown Author, (1999, May). Companion Planting. Cornell University Cooperative Extension. https://extension.unl.edu/statewide/lincolnmcpherson/Cornell%20Guide%20to% 20Companion %20Planting.pdf.
[4] Riotte, L. (1998). Carrots Love Tomatoes: Secrets of Companion Planting for Successful Gardening (2nd ed.). Storey Publishing, LLC.
