What is the best companion plant for tomatoes
Discover the best companion plants for tomatoes, including basil, marigolds, and more. Learn what works, what doesn't, and how to plant them for a healthier garden.
The best companion plant for tomatoes is basil. It repels thrips and other pests, improves flavor, and grows well with tomatoes in the same conditions. Plant basil 12 inches away from tomato stems, and you’ll see fewer pest problems and better use of space.
Why basil works
Basil’s strong scent confuses pests like thrips, aphids, and spider mites, which are common tomato enemies. It also attracts pollinators and beneficial insects that prey on tomato ho
rnworms. While “improved flavor” is often overstated, many gardeners swear by the pairing, and the practical benefits are real.
Other proven companions
- Marigolds: French marigolds (Tagetes patula) release chemicals from their roots that suppress nematodes in the soil. Plant them 12 inches from tomato stems. They also attract hoverflies, which eat aphids.
- Garlic and onions: Their strong smell repels spider mites and aphids. Plant garlic cloves 6 inches apart between tomato rows, or onions 4 inches apart as a border.
- Nasturtiums: These act as a trap crop for aphids, drawing them away from tomatoes. Plant them at the edge of the bed, 12 inches from tomatoes.
- Parsley: Attracts hoverflies and other beneficial insects. It also fills in gaps, suppressing weeds.
What to avoid
- Brassicas (cabbage, broccoli): They compete for nutrients and can stunt tomato growth.
- Fennel: It secretes chemicals that inhibit tomato growth.
- Corn: Attracts corn earworm, which also attacks tomatoes.
- Potatoes: They share blight and other diseases, so keep them separated.
How to plant companions
- Spacing: For basil, plant 12 inches from tomato stems, with 18 inches between basil plants. For marigolds, 12 inches apart. For garlic, 6 inches apart in rows between tomatoes.
- Timing: Plant basil and marigolds at the same time as tomatoes, after the last frost. Garlic goes in the fall for a spring harvest, or in early spring in zones 8 and warmer.
- Soil: All these companions prefer well-drained soil with a pH of 6.0 to 7.0, same as tomatoes. Add compost before planting.
- Maintenance: Keep companions pruned so they don’t shade tomatoes. Basil can be pinched back to encourage bushiness.
Planting schedule by zone
| USDA Zone | Last frost date | Plant tomatoes and basil |
|---|---|---|
| 3-4 | May 15-30 | June 1-15 |
| 5-6 | April 15-May 15 | May 15-June 1 |
| 7-8 | March 15-April 15 | April 1-15 |
| 9-10 | February 1-March 1 | March 1-15 |
Realistic expectations
Companion planting is not a magic bullet. You’ll still need to water, fertilize, and watch for pests. But with basil and marigolds, you can reduce pest pressure by 30-50% in my experience. Expect to spend $3-$5 for a basil plant or $2-$4 for a packet of seeds. Marigold seeds run $2-$4 per packet.
FAQ
Can I plant basil in the same pot as tomatoes? Yes, but use a container at least 18 inches wide and 18 inches deep. Plant basil at the edge, 6 inches from the tomato stem. This works well on patios.
Do marigolds really repel nematodes? French marigolds release compounds that suppress root-knot nematodes, but only if planted densely (6 inches apart) and allowed to grow for at least 60 days before tomatoes. In most home gardens, they help but don’t eliminate the problem.
What is the best companion for tomatoes in containers? Basil is the best for containers because it doesn’t compete for root space. Use a 5-gallon pot for the tomato and a 1-gallon pot for basil, placed nearby.
Can I plant tomatoes with peppers? Yes, peppers are good companions. They have similar needs and don’t compete heavily. Just give them 18 inches of space between plants.
The bottom line
For most gardeners, basil is the best companion plant for tomatoes. It’s easy to grow, repels common pests, and doesn’t compete for nutrients. Add marigolds for nematode suppression, and avoid brassicas and fennel. Plant them at the right time for your zone, and you’ll have a healthier, more productive tomato patch. Start with basil this season; it’s the simplest, most effective choice.