February 28, 2026

Companion Planting Chart for Vegetables

Companion planting is one of those gardening topics where folk wisdom and actual science mix together in confusing ways. Some pairings are backed by solid research. Others have been repeated in gardening books for decades without much evidence. I'll give you the chart first, then break down what we actually know and what's just tradition.

The quick reference chart

What companion planting actually does

The science behind companion planting falls into a few categories:

Pest management

This is where the strongest evidence exists. Certain plant combinations genuinely reduce pest problems:

• Marigolds and nematodes: French marigolds (Tagetes patula) produce compounds that suppress root-knot nematodes in soil. This is well-documented in university research. Plant them anywhere you've had nematode issues.
• Onions and carrot fly: The strong scent of onions masks the smell of carrots, making it harder for carrot flies to locate their target. Interplanting rows of each works well.
• Basil and tomato hornworm: Less scientifically rigorous, but many gardeners report fewer hornworms near basil. The aromatic oils may confuse moths looking for a place to lay eggs.
• Nasturtiums as trap crops: Aphids prefer nasturtiums over most vegetables. Plant them on the border to draw aphids away from your crops.

Nitrogen fixing

Legumes (beans, peas, clover) pull nitrogen from the air and fix it in the soil through symbiotic bacteria in their root nodules. This is real, measurable, and significant. But here's the catch: most of that nitrogen becomes available after the legume dies and decomposes, not while it's actively growing.

The Three Sisters planting (corn, beans, squash) works partly because of this — though the bigger benefit is structural. Corn provides a trellis for beans, beans fix nitrogen, and squash shades the ground to suppress weeds and retain moisture. For more details, see our guide on How to plan a vegetable garden.

Space efficiency

Some companion planting is just smart use of space: For more details, see our guide on USDA hardiness zone map explained.

• Radishes between rows of slow-growing carrots. The radishes are harvested before the carrots need the space.
• Lettuce under tall tomato plants. The tomatoes provide afternoon shade that prevents bolting.
• Quick-maturing spinach between pepper transplants. Harvested before peppers size up.

What to be skeptical about

Some companion planting claims are repeated everywhere but lack solid evidence:

• "Tomatoes and basil grow better together": They're good neighbors (similar growing conditions), and basil may deter some pests, but there's no evidence they enhance each other's growth or flavor.
• "Don't plant tomatoes near potatoes": This one is actually true — but not because of allelopathy. Both are solanaceae and share diseases. Late blight can jump between them.
• "Fennel inhibits everything": Fennel does produce allelopathic compounds, but the effect is modest unless you're growing it right next to other crops. Giving it 3-4 feet of buffer is enough.

Practical companion planting layouts

Here are three garden bed layouts that apply companion planting principles:

Bed 1 — The Classic Kitchen Garden (4'x8'):

• Row 1: Tomatoes (3 plants, 24" apart) with basil between each
• Row 2: Peppers (4 plants) with onions on both sides
• Row 3: Lettuce and carrots, alternating rows
• Border: Marigolds on all edges

Bed 2 — Three Sisters (4'x8'):

• Center mounds: 3 corn plants per mound, 3 mounds total
• Around each mound: 3-4 bean seeds
• Between mounds: 1 squash or pumpkin plant

Bed 3 — Cool Season (4'x8'):

• Row 1: Broccoli (3 plants) with dill between
• Row 2: Onions and carrots, alternating
• Row 3: Peas on a short trellis with radishes at the base
• Row 4: Lettuce succession planting

Once you've figured out your layout, use the planting calendar to time everything correctly. And for help figuring out what to grow in the first place, check out our vegetable garden planning guide.