Emily ParkerBy Emily Parker

Updated November 2026

A tomatoes companion planting chart tells you which crops grow well beside your tomatoes and which ones compete with them or attract trouble. Use it to plan your bed layout before transplanting, so you can pair tomatoes with basil, carrots, onions and marigolds while keeping them away from potatoes, fennel and brassicas. The sections below explain how to read a chart, build your own, and avoid the common mistakes that cancel out the benefits.

What a Tomato Companion Planting Chart Shows

Most charts sort plants into three groups: good neighbors, poor neighbors, and neutral plants. Good neighbors may repel pests, attract pollinators, provide shade or support, or use different soil layers so they do not compete. Poor neighbors often share the same diseases, pull the same nutrients, or release compounds that slow growth. Neutral plants can go either way depending on spacing and watering.

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Treat any chart as a starting point rather than a rulebook. Evidence for many pairings is anecdotal, and results depend on your climate, soil and pest pressure.

Best Companions for Tomatoes

These pairings are the ones gardeners most often recommend for tomatoes:

  • Basil: Commonly planted alongside tomatoes, with the idea that its scent may deter some pests. Plant it 12 to 18 inches from the tomato stem.
  • Carrots: Their root zone differs from tomatoes, so they do not compete much. Sow carrots 2 inches apart in the spaces between tomato plants.
  • Onions and garlic: Their strong smell is often credited with reducing some aphids. Space bulbs 4 to 6 inches apart at the bed edge.
  • Marigolds: Frequently used as trap or border plants. Place one every 2 to 3 feet along the bed.
  • Parsley: Attracts beneficial insects such as hoverflies. Plant 8 to 10 inches from tomato stems.
  • Nasturtiums: Serve as a trap crop for aphids. Plant at the bed edge where they can draw pests away.

Plants to Keep Away from Tomatoes

Some crops either compete with tomatoes or share diseases with them. Keep these at least 3 feet away, or in a separate bed:

  • Potatoes: Share early blight and late blight, and both draw on the same soil nutrients.
  • Fennel: Its growth can suppress tomato development, so give it its own space.
  • Brassicas (cabbage, broccoli, kale): Heavy feeders that compete for nitrogen and calcium.
  • Corn: Taller corn can shade tomatoes and attract shared pests like corn earworm. Use caution when planting them close together.

How to Build Your Own Chart for Your Garden

A custom chart works better than a generic one because it reflects your space and pests. Start by listing the crops you already grow, then mark each pairing as good, poor or neutral based on your notes from past seasons.

  1. List your tomato varieties and the number of plants you intend to grow.
  2. Note which pests and diseases you have seen before, such as hornworms, aphids or early blight.
  3. Sketch the bed layout on graph paper, marking each plant at its mature spacing.
  4. Assign a companion or conflict rating to each neighboring pair.
  5. Review the layout each season and adjust based on what happened.

Spacing Guidelines

Spacing matters as much as pairing. Overcrowding reduces airflow, which raises the risk of fungal disease. Use this rough guide:

Crop Distance from tomato stem
Basil 12 to 18 inches
Parsley 8 to 10 inches
Carrots 2 inches between plants, at the bed edge
Marigolds 2 to 3 feet apart along the bed

Common Mistakes to Avoid

  • Planting basil too close to the tomato stem, which crowds the root zone.
  • Mixing tomatoes and potatoes in the same bed because both are nightshades and share diseases.
  • Ignoring airflow and planting companions so densely that leaves stay wet.
  • Expecting companions to replace pest control. Check plants regularly and handpick hornworms.
  • Following a chart without observing your own garden. Keep notes to refine your choices.

A sturdy support system keeps tomatoes off the soil and makes spacing easier to maintain. Tomato cages and stakes work well with interplanted herbs and flowers. View on Amazon

Row markers help you keep companions at the right distance, especially in a square foot or intensive layout. View on Amazon

FAQ

Can I plant basil and tomatoes together every year?

Yes, and many gardeners do. Rotate the bed location each season if you are concerned about soilborne disease buildup.

Are marigolds really effective against tomato pests?

Marigolds are widely recommended as companions, but evidence is mixed. Treat them as one tool alongside regular scouting and handpicking.

What is the single worst companion for tomatoes?

Potatoes are usually the top pick to avoid, because they share early and late blight. Keep them in separate beds.

Conclusion

A tomatoes companion planting chart gives you a clear starting layout, but your own observations matter most. Pair tomatoes with basil, carrots and marigolds, keep potatoes and brassicas apart, and respect spacing for airflow. Update your chart after each season to build a plan that fits your garden.

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Emily Parker

About Emily Parker

Emily Parker is part of our editorial team and reviews and edits our vegetable & edible gardening guides, checking product details against manufacturer specifications and owner feedback.