Plant basil, parsley, marigold, and borage near your tomatoes to improve growth and pest control

Certain herbs and flowers grown alongside tomatoes can reduce pest damage, improve pollination, and make better use of garden space. Basil is the most reliable choice—it repels spider mites and whiteflies while its scent may confuse insects looking for tomato plants. Parsley attracts beneficial insects that prey on tomato pests. Marigolds deter nematodes in the soil and some above-ground pests. Borage brings pollinators and can be harvested for tea or salads.

These plants thrive in the same conditions as tomatoes: full sun, consistent moisture, and warm soil. They do not compete heavily for nutrients when spaced correctly, and most can be planted at the same time as your tomato seedlings or seeds.

Key Takeaways

  • Basil planted within 12 inches of tomato stems repels spider mites and whiteflies while remaining straightforward to harvest for cooking.
  • Parsley and borage attract hoverflies and other beneficial insects whose larvae feed on common tomato pests like aphids.
  • Marigolds reduce root-knot nematode damage in soil and should be planted around the base of tomato plants rather than directly touching the stem.
  • Space companion herbs 8 to 12 inches from the tomato stem to avoid shading the lower leaves and competing for water at the root zone.
  • Avoid planting brassicas (cabbage, broccoli) or fennel near tomatoes, as they inhibit tomato growth and attract different pests.

Basil: The Most Effective Tomato Companion

Basil is the top choice for tomato gardens because it repels two of the most common tomato pests—spider mites and whiteflies. Plant basil seedlings or seeds 8 to 12 inches away from the tomato stem once soil temperatures reach 60°F. Basil grows quickly and will reach harvest size (6 to 8 inches tall) in 3 to 4 weeks.

Pinch off the top leaves regularly to encourage bushier growth and prevent flowering, which reduces the plant's pest-repelling oils. You can harvest basil continuously throughout the growing season for cooking. If basil flowers do appear, the plant is still useful—the flowers attract pollinators—but the leaves become less flavorful.

Basil needs the same watering schedule as tomatoes: about 1 inch per week, or more in hot weather. Water at the soil level rather than overhead to prevent fungal disease on both plants. In cooler climates, basil may need to be replanted mid-season if the first planting slows in late summer.

Parsley and Borage for Beneficial Insects

Both parsley and borage attract hoverflies, parasitic wasps, and other predatory insects whose larvae consume aphids, mites, and other tomato pests. Parsley is a biennial that grows slowly in its first year but produces abundant foliage. Borage is an annual with blue flowers and fuzzy leaves that bees and hoverflies visit constantly.

Plant parsley seedlings 10 to 12 inches from the tomato stem in early spring. Parsley tolerates partial shade better than basil, so it can be placed on the east or west side of a tall tomato plant. Harvest outer stems first, leaving the center to grow. Parsley reaches full size in 6 to 8 weeks and produces for the entire season.

Borage seeds can be sown directly into the soil 12 inches from the tomato stem after the last frost. It germinates in 7 to 10 days and flowers within 4 to 6 weeks. Borage self-seeds readily, so if you let one plant flower and drop seeds, you may have volunteers the following year. The leaves and flowers are edible and taste like cucumber.

Marigolds for Soil and Pest Protection

Marigolds reduce root-knot nematode populations in soil, a microscopic pest that damages tomato roots and stunts growth. Plant marigold seedlings around the base of tomato plants, spacing them 8 to 10 inches from the stem. Marigolds bloom within 4 to 6 weeks and flower continuously until frost.

Marigolds also deter some above-ground pests like spider mites and whiteflies, though less reliably than basil. Their bright orange or yellow flowers attract pollinators and look attractive in the garden. Deadhead spent flowers (pinch them off) every 3 to 4 days to keep blooms coming and prevent the plant from going to seed too early.

Marigolds are drought-tolerant once established, so they need less frequent watering than tomatoes. If your tomato bed dries out quickly, marigolds can actually help by shading the soil and reducing evaporation. They thrive in full sun and poor soil, making them useful in gardens where the tomato bed has been heavily amended.

Spacing and Planting Timing

Plant companion herbs at the same time as your tomato seedlings or within 1 to 2 weeks after transplanting. This timing allows all plants to establish roots together and reach mature size at roughly the same pace. If you plant herbs too early, they may shade the young tomato seedling; if too late, they will not reach useful size before pests arrive.

Space herbs 8 to 12 inches from the tomato stem, measured from the center of the tomato plant outward. This distance prevents the herb from shading the lower tomato leaves (which need sun for photosynthesis) while keeping it close enough to affect pest behavior. If your tomato variety grows to 6 feet or taller, you can plant herbs slightly closer because the lower leaves will receive dappled light rather than full shade.

In containers, space is tighter. A 5-gallon pot can hold one tomato plant and one basil plant 6 to 8 inches apart. Larger containers (10 gallons or more) can accommodate a tomato and two companion herbs. Water container plants more frequently than in-ground plants because soil dries faster.

Herbs to Avoid Near Tomatoes

Fennel and brassicas (cabbage, broccoli, kale, cauliflower) inhibit tomato growth and should not be planted nearby. Fennel releases compounds that suppress the growth of many plants, including tomatoes. Brassicas attract different pests and compete for the same nutrients, reducing yield in both crops.

Mint spreads aggressively through underground runners and will overtake a tomato bed if not contained. If you want to grow mint nearby, plant it in a separate pot or use a root barrier (a buried plastic or metal edge) to prevent it from spreading into the tomato area. Dill can attract hornworms, the large green caterpillars that eat tomato foliage, so it is best grown away from tomatoes.

Watering and Feeding Companion Herbs

Most companion herbs need the same watering schedule as tomatoes: about 1 inch per week from rain or irrigation. Water deeply and less frequently rather than shallow and often, which encourages deep root growth and drought tolerance. Water at soil level in the early morning to reduce disease risk.

Basil, parsley, and borage benefit from a light feeding every 3 to 4 weeks with a balanced fertilizer (equal nitrogen, phosphorus, and potassium). Marigolds need little to no fertilizer and may produce fewer flowers if overfed. If you are already fertilizing tomatoes, you can explore the same fertilizer to herbs at half strength, or skip herbs entirely and let them draw nutrients from the tomato bed.

Harvesting Herbs While Tomatoes Grow

Begin harvesting basil and parsley once they reach 6 inches tall, usually 3 to 4 weeks after planting. Pinch off the top 2 to 3 inches of stem, which encourages bushier growth and delays flowering. Regular harvesting keeps plants compact and productive throughout the season.

Borage flowers can be harvested as soon as they open and used fresh in salads or drinks. The leaves are edible but hairy and best used when young and tender. Marigold flowers are edible and can be harvested at any stage of bloom, though they taste slightly bitter. Harvest marigold petals in the morning after dew dries but before the sun gets hot.

Harvesting companion herbs does not reduce their pest-control benefits. In fact, regular harvesting keeps plants healthy and vigorous, which strengthens their natural defenses. You can harvest herbs right up until frost or until you stop harvesting tomatoes.

Frequently Asked Questions

Can I plant herbs and tomatoes in the same pot?

Yes, if the pot is large enough. A 10-gallon container can hold one tomato plant and one basil plant with 6 to 8 inches between them. Smaller pots (5 gallons) work for one tomato and one herb, but you will need to water more frequently because soil dries faster. Use high-quality potting soil, not garden soil, to may support good drainage.

Do companion herbs actually reduce pests, or is it just a myth?

Basil and marigolds have documented effects on spider mites, whiteflies, and nematodes in research trials. Parsley and borage work mainly by attracting beneficial insects rather than repelling pests directly. Results vary by climate, pest pressure, and how consistently you maintain the plants, so companion herbs work best as part of a broader pest management approach, not as a complete solution.

What if I forget to harvest basil and it flowers?

Flowering basil is still useful—the flowers attract pollinators and the plant continues to repel some pests. However, the leaves become less flavorful and the plant puts energy into seed production rather than leaf growth. Pinch off flower buds as soon as you see them to keep the plant in leaf-production mode, or let it flower if you want seeds for next year.

Can I plant herbs in spring and expect them to last until tomato harvest?

Basil, borage, and marigolds are annuals and will grow from spring through fall frost. Parsley is a biennial and will produce leaves for the entire first season. In warm climates (zones 9 and above), basil may slow down in mid-summer heat; replanting in late summer gives you fresh plants for fall tomatoes. Borage and marigolds tolerate heat better and often produce more flowers in hot weather.

Should I remove companion herbs before harvesting tomatoes?

No. Companion herbs can remain in the bed until frost kills them or until you pull out the tomato plants. They continue to suppress pests and attract pollinators right up until the end of the season. If an herb becomes diseased or infested, remove it to prevent the problem from spreading to the tomato plant.