Companion Planting Chart: What to Plant Together (and What to Keep Apart)

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Show me the neighbors for

TrialedPracticalTraditional what these tags mean

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The full chart — 20 crops, friends and enemies

Every pairing below carries its evidence tag. This is the same data the picker uses, all in one place.

Crop	Good neighbors	Keep apart from
Tomatoes	Basil^tr, Onion family^tr, Carrots^tr, Lettuce^P, Sweet alyssum^T, French marigolds^T	Potatoes, Corn, Fennel, Cabbage family, Black walnut trees
Peppers	Basil^tr, Onion family^tr, Sweet alyssum^T	Fennel, Black walnut trees
Eggplant	Beans^tr, French marigolds^tr, Sweet alyssum^T	Potatoes, Black walnut trees
Potatoes	Beans^tr, Cabbage family^tr, Corn^tr, Horseradish^tr	Tomatoes, Squash & cucumbers, Sunflowers, Black walnut trees
Beans bush & pole	Corn^P, Squash^P, Cucumbers^tr, Radishes^tr, Summer savory^tr	Onion family
Peas	Carrots^tr, Radishes^tr, Cucumbers^tr, Lettuce^P	Onion family
Carrots	Onion family^T, Peas^tr, Lettuce^P, Radishes^P	Dill
Beets	Onion family^tr, Cabbage family^tr, Lettuce^P, Bush beans^tr	Pole beans
Radishes	Carrots^P, Peas^tr, Lettuce^P, Cucumbers^tr	—
Onion family onions, garlic, leeks, chives	Carrots^T, Beets^tr, Lettuce^tr, Cabbage family^tr, Tomatoes^tr	Beans, Peas
Lettuce	Carrots^tr, Radishes^P, Strawberries^tr, Tomatoes or corn^P, Sweet alyssum^T	—
Spinach	Strawberries^tr, Peas^P, Radishes^P	—
Cabbage family broccoli, cabbage, kale, Brussels sprouts, cauliflower	Dill^T, Aromatic herbs (sage, rosemary, mint)^T, Radish or mustard trap strip^T, Nasturtiums^tr, Beets^tr, Onion family^tr, Potatoes^tr	Strawberries, Tomatoes, Pole beans
Squash & pumpkins zucchini too	Corn^P, Beans^P, Radishes^tr, Nasturtiums^tr, Blue hubbard squash (trap crop)^T	Potatoes
Cucumbers	Beans^tr, Corn^P, Peas^tr, Radishes^tr, Sunflowers^tr	Potatoes, Strong aromatic herbs (sage)
Corn	Beans^P, Squash & pumpkins^P, Cucumbers^tr, Peas^tr, Potatoes^tr	Tomatoes
Basil	Tomatoes^tr, Peppers^tr	—
Strawberries	Bush beans^tr, Spinach^tr, Lettuce^tr, Borage^tr	Cabbage family
Melons cantaloupe, muskmelon	Corn^tr, Sunflowers^tr	Potatoes

Tags: T = trialed (research behind the mechanism) · P = practical (space-and-light logic) · tr = traditional (chart canon, thin evidence). The picker above gives you the why for every pairing.

How to read this chart

"Companion planting" covers four different things that get lumped together: pest confusion (mixed smells and shapes make your crop harder to find), trap cropping (a sacrificial plant pulls the pests off the one you care about), shade sharing (tall crop shelters heat-shy crop), and flowers that feed the insects that eat your pests.

The tags tell you how much weight each pairing can hold. Trialed means there's real research behind the mechanism. Practical means it's plain space-and-light logic — no study needed to know lettuce likes shade in July. Traditional means it's been on the charts for decades with thin evidence either way. Fine to follow when it's easy. Not worth re-planning a bed over.

And the honest caveat that outranks the whole chart: sun, water, and spacing matter more than any pairing. A basil plant crammed against a tomato stem helps nobody — work out how far apart to plant them first, then pick the neighbors.

The pairings that actually earn their spot

If you only take four things from the research, take these:

Flowers that feed the good bugs. Sweet alyssum's little flowers feed hoverflies, and hoverfly larvae eat aphids. Commercial lettuce growers in Salinas interplant it on purpose. It works next to any crop that gets aphids.
Mixed smells around brassicas. Strong-smelling herbs (sage, rosemary, mint in a pot) interplanted with cabbage-family crops make them harder for pests to find. Real research, modest effect.
Trap crops. A sacrificial blue hubbard squash at the bed edge pulls cucumber beetles off your main planting. A radish-and-mustard strip pulls flea beetles off young brassicas — mixes of three-plus trap species beat any single one.
Dill flowers near the cabbage bed. Let some dill bloom: its flowers feed the tiny parasitoid wasps that hunt cabbage worms. (Just keep mature dill away from the carrot row.)

basil interplanted between tomato plants real photo — alt: "Basil interplanted between tomato plants in a raised garden bed"

What not to plant together

The short list that's actually consistent across the charts:

Keep apart	Why
Fennel + almost everything	The chart canon's one true loner. Nobody lists it as a good neighbor. Give it its own pot.
Onion family + beans or peas	The most consistent "no" in companion planting. Unproven mechanism, unanimous canon — separate rows.
Potatoes + tomatoes	Same family, same late blight. One sick bed infects the other.
Corn + tomatoes	Corn earworm and tomato fruitworm are the same moth. Side by side, you set its table twice.
Any vegetable bed + black walnut	Walnut roots release juglone; tomatoes, peppers, potatoes, and eggplant are all on the sensitivity list. Keep beds clear of the canopy.

fennel alone in its own pot, away from the bed real photo — alt: "Fennel growing in its own separate container away from the vegetable bed"

Companion planting by crop

Tomatoes. Basil and alliums by tradition, lettuce for the shade trade, alyssum for the aphid patrol. The real rules are the don'ts: no potatoes, no corn, no fennel.

Peppers. Same playbook as tomatoes, smaller plant. Basil and onions alongside; alyssum nearby earns its spot the same way.

Squash and zucchini. The Three Sisters ground floor — under corn with beans climbing above. The trialed trick: one sacrificial blue hubbard at the edge as a beetle magnet.

Carrots. Interplanted onions confused carrot rust fly in some trials, did nothing in others. Radishes mark the row and leave early. Keep mature dill out of it.

Beans. Corn is the original trellis, squash is the living mulch. The one rule every chart agrees on: no onions, garlic, or chives in the row.

FAQ

What should you not plant together?

The consistent ones: fennel near almost anything, onions and garlic near beans or peas, potatoes near tomatoes (they share late blight), and any vegetable bed under a black walnut tree. Most other "never plant" rules are folklore. These four show up on every chart for a reason.

Does companion planting actually work?

Some of it. Trap crops, mixed strong-smelling plantings that confuse pests, and flowers that feed pest-eating insects have real research behind them. Most classic pairings don't — they're tradition, not trials. That's why every pairing in this chart carries a tag telling you which kind it is.

What grows well with tomatoes?

Basil and the onion family are the classic picks. Lettuce earns its spot practically — it wants the summer shade a tall tomato throws. Sweet alyssum nearby feeds hoverflies whose larvae eat aphids. Keep tomatoes away from potatoes, corn, and fennel.

How far apart should companion plants be?

Use the normal spacing for each crop — companion planting means sharing a bed, not crowding. A basil plant still wants its foot of space next to a tomato. The plant spacing calculator works out the numbers for your bed size.

Sources

The pairings and their tags trace to these. When a claim couldn't be sourced, it didn't make the chart.

West Virginia University Extension — Companion Planting The classic companions-and-incompatibles chart. Most rows tagged traditional trace here.
University of Minnesota Extension — Companion planting in home gardens The evidence review behind our tags: which trap crops hold up (blue hubbard, multi-species flea-beetle strips), how pest-confusing interplanting works, and which folklore claims don't survive testing.
Penn State Extension — Landscaping and Gardening Around Walnuts and Other Juglone Producing Plants The black-walnut rule: juglone from walnut roots, and which crops tolerate it.
USDA Agricultural Research Service (Salinas, CA) — Strip-intercropping research on sweet alyssum in commercial lettuce (Eric Brennan) Where the alyssum-hoverfly pairing earns its trialed tag — it's standard practice in organic lettuce fields.

This chart's free and it stays free. No signup, no wall.

The chart tells you what goes together. Knowing when to start each of these from seed — and what to do after they're in the ground — is the part we're building GardenTrack for. It'll remember what you planted and where, then tell you what to do and when. Coming spring 2027. Want a heads-up? Join the waitlist.