Full Companion Planting Chart

Plant with

• Basil^T — The 'basil makes tomatoes taste better' legend is unproven — a three-year double-blind trial at West Virginia University found no flavor difference. But basil earns its spot another way: Minnesota Extension reports basil can help cut thrips on tomatoes, and a modest yield bump shows up at good density. Same heat and water, so it costs you nothing.
• Onion family^tr — On every chart, no trial behind it — and nothing against it. Plant them together if it suits the bed; expect neither harm nor magic.
• Carrots^tr — 'Carrots Love Tomatoes' is a book title, not a trial. They coexist fine — just expect the tomato to shade the carrots by August.
• Lettuce^P — A tall tomato throws exactly the shade lettuce wants once summer heat pushes it to bolt.
• Sweet alyssum^T — Its flowers feed hoverflies, whose larvae eat aphids — documented biocontrol that organic lettuce growers use on purpose (USDA-ARS). It guards any aphid-prone crop, tomatoes included.
• French marigolds^T — Real, but misunderstood: French marigold roots release a nematode-killing compound — only when grown as a dense stand for a couple of months before the crop (UF/IFAS). A few tucked between tomatoes are decoration, not pest control.

Keep apart from

• Potatoes — Same family, same late blight — the disease moves both directions. One sick bed infects the other.
• Corn — Corn earworm and tomato fruitworm are the same moth. Side by side, you set its table twice.
• Fennel — Fennel is genuinely allelopathic: its foliage and seeds are rich in compounds (chiefly trans-anethole) that suppress the germination and growth of many plants in the lab. Whole-plant effects at garden spacing are milder than the "fennel kills everything" lore, but the chemistry is real — give it its own pot.
• Cabbage family — Both are heavy nitrogen feeders, so crowding them shortchanges both — that's the real reason to give them room, not the chart's vague 'they clash.' No evidence brassicas chemically stunt tomatoes.
• Black walnut trees — Walnut roots release juglone, and tomatoes are on every sensitivity list (Penn State). Keep beds well clear of the canopy and root zone.

Plant with

• Basil^tr — Same bed conditions, same kitchen. Thin evidence for any plant-health effect, but zero downside and dinner grows in one place.
• Onion family^tr — Chart canon, nothing more — but nothing against it either.
• Sweet alyssum^T — The hoverfly trick works next to any crop that gets aphids, and peppers do.

Keep apart from

• Fennel — Fennel is allelopathic (documented trans-anethole chemistry that curbs nearby seedlings). Give it its own pot.
• Black walnut trees — Peppers are nightshades too — juglone hits them like it hits tomatoes.

Plant with

• Beans^tr — An old chart pick with thin evidence — but eggplant and beans share a season with no conflict, so it's a safe pairing.
• French marigolds^tr — Charted as a beetle repellent, but Minnesota Extension found no research for that. Their one proven trick — killing root-knot nematodes — needs a dense pre-crop stand, not a few tucked in. Treat interplanted marigolds as decoration that might help.
• Sweet alyssum^T — Flowers for the aphid-eaters — the mechanism doesn't care which crop it's guarding.

Keep apart from

• Potatoes — Colorado potato beetles love eggplant even more than potatoes. Next to a potato patch, your eggplant takes the worst of the swarm.
• Black walnut trees — Nightshade again — juglone-sensitive.

Plant with

• Beans^tr — On the charts for generations. Beans fix their own nitrogen and don't compete hard — easy neighbors, no proven bonus.
• Cabbage family^tr — Chart canon. The practical bit is shared cool-season timing; both are hungry, so feed the bed.
• Corn^tr — Different families, different main pests — they just coexist. Two heavy feeders, so keep the soil rich.
• Horseradish^tr — Planted at potato-patch corners for generations to 'ward off bugs.' Tradition, no trial — and horseradish is an aggressive perennial, so give it a permanent edge, never the middle of the bed.

Keep apart from

• Tomatoes — Late blight runs both directions between these two. Keep them apart.
• Squash & cucumbers — Both are big, heavy feeders fighting for space, water, and nutrients — and hilling potatoes tears up shallow cucurbit roots. The chart's 'they trade diseases' story is mostly wrong (potato late blight can't infect squash or cukes). Separate them for room, not for disease.
• Sunflowers — Two real strikes: sunflowers are allelopathic (roots and residues release compounds that curb neighbors), and they grow tall, thirsty, and heavy-rooted — shading and starving a potato patch. Plant them at the garden edge.
• Black walnut trees — Potatoes are juglone-sensitive. Don't fight a walnut tree for that ground.

Plant with

• Corn^P — The original living trellis — pole beans climb the stalks. Skip the myth that the beans feed the corn the same year (most of that nitrogen only reaches the soil after the plants die back); the free trellis is the real payoff.
• Squash^P — The third Sister. Its big leaves are a living mulch that shades soil and suppresses weeds under the corn and beans.
• Cucumbers^tr — Chart canon; they share a season and stay out of each other's way.
• Radishes^tr — Old chart pairing. Radishes are gone before beans need the room anyway.
• Summer savory^tr — The bean herb on every old chart. Untested, but cook with it and the pairing pays either way.

Keep apart from

No real enemies. The famous 'never near onions' rule is folklore — see below.

Plant with

• Carrots^tr — Long-standing chart pairing — both like cool weather and loose soil.
• Radishes^tr — Same cool season, zero competition. In and out before peas fill in.
• Cucumbers^tr — On the classic charts. Peas finish about when cucumbers get going.
• Lettuce^P — Cool-season bedmates on the same watering schedule.

Keep apart from

No real enemies on the list. The old "keep away from onions" flag is unsupported — see below.

Plant with

• Onion family^T — Interplanted onions can mask the carrot's scent and throw off the carrot rust fly — real in controlled trials, but patchy: it only holds while the onions are actively growing and outnumber the carrots. Worth a try, not a shield.
• Peas^tr — The classic cool-season pair — both like loose soil.
• Lettuce^P — Quick lettuce fills the row while slow carrots take their time.
• Radishes^P — Radishes sprout in days, mark your carrot row, and are gone before carrots need the space.

Keep apart from

• Dill — The real reason isn't the chart's 'dill stunts carrots' (no trial shows that, and the two can't cross-pollinate — they're different plants entirely). It's that both are in the carrot family and both feed the carrot rust fly, so planting them together concentrates that pest. Keep flowering dill a bed away.

Plant with

• Onion family^tr — Listed together on the classic charts, and they share space politely.
• Cabbage family^tr — Chart canon — beets sit on the cabbage family's companion list, both cool-season.
• Lettuce^P — Shallow roots next to deep ones. No fight over the same layer of soil.

Keep apart from

No real enemies. The charted "pole beans" feud is folklore — see below.

Plant with

• Carrots^P — Row marker, soil breaker, and harvested before carrots wake up.
• Peas^tr — Cool-season chart canon.
• Lettuce^P — Both fast, both shallow, both out of each other's way.
• Cucumbers^tr — On the classic charts as a cucumber companion.

Keep apart from

No real enemies. Radishes are in and out in a month — most garden feuds take longer than that.

Plant with

• Carrots^T — The carrot-fly scent-masking trick — real in trials, patchy in practice, no downside in the bed.
• Beets^tr — Chart canon, both directions.
• Lettuce^tr — On the classic charts — lettuce's own row lists onions.
• Cabbage family^tr — Old chart pairing; both hold cool-season beds.
• Tomatoes^tr — Canon on the classic charts, no conflict.

Keep apart from

No real enemies. The famous "never near beans or peas" rule is unsupported — see below.

Plant with

• Carrots^P — Quick lettuce fills the row while slow carrots take their time, and both like cool weather.
• Radishes^P — Quick, shallow, and gone. Easy neighbors.
• Strawberries^tr — Straight off the WVU chart — lettuce works as a strawberry border.
• Tomatoes or corn^P — Summer shade from a tall neighbor keeps lettuce from bolting a bit longer.
• Sweet alyssum^T — The real thing: Salinas lettuce growers interplant alyssum so its hoverflies handle the aphids (USDA-ARS, UC IPM).

Keep apart from

Nothing on the enemies list worth your worry. Just don't make it fight a thirsty giant for water.

Plant with

• Strawberries^tr — The strawberry chart lists spinach as a companion. Canon both ways, no conflict.
• Peas^P — Same cool season, and pea shade stretches spinach a little deeper into spring.
• Radishes^P — Quick, shallow, gone. No competition.

Keep apart from

No flagged enemies on the classic charts. Spinach's real enemy is summer heat.

Plant with

• Dill (flowering)^T — Let some dill bloom nearby: its tiny open flowers feed the parasitoid wasps that hunt cabbageworms. The mechanism is well documented; how much a few plants cut damage at garden scale is less measured.
• Leafy companions & aromatic herbs^T — Interplanting cabbage among other low, leafy plants really does cut pest damage — but not by "repelling with smell," which controlled trials debunked. Pests land on any green surface and get confused by the clutter (the "appropriate/inappropriate landing" effect), so any leafy groundcover works about as well as fragrant herbs.
• Radish or mustard trap strip^T — A border strip of pungent mustard or daikon, sown a week or two early, pulls flea beetles off your seedlings — give it about a tenth of the space. Mixes of three-plus trap species beat any single one.
• Nasturtiums^tr — On the companion lists with an aphid-magnet reputation. If aphids pile onto them, pull those plants before they breed and spread.
• Beets^tr — On the classic chart's companion list for the cabbage family.
• Onion family^tr — Chart canon; comfortable cool-season neighbors.
• Potatoes^tr — Old chart pairing; shared cool-season timing.

Keep apart from

• Tomatoes — Both are heavy nitrogen feeders, so crowding them shortchanges both. Give them room or separate beds — for the feeding, not for a chemical grudge (there isn't one).

Plant with

• Corn^P — Three Sisters ground floor: squash leaves are the living mulch that shades soil and holds moisture.
• Beans^P — The Sisters again — beans overhead, squash below.
• Nasturtiums^T — Research-backed, not just pretty: interplanted nasturtiums reduced squash bug numbers, and with marigold cut both squash bug and cucumber beetle damage (Minnesota Extension).
• Sweet alyssum^T — Its flowers pull in the natural enemies of aphids — Minnesota Extension found alyssum raised beneficial-insect numbers around squash.
• Blue hubbard squash (trap crop)^T — A sacrificial blue hubbard planted as a border pulls striped cucumber beetles off your squash — Connecticut trials cut beetle damage on the protected crop by up to ~95%, often beating full-field spraying.
• Radishes^tr — On the WVU chart's squash row.

Keep apart from

• Potatoes — Two sprawling heavy feeders fighting for space and nutrients, and hilling potatoes disturbs shallow squash roots. Separate them for room, not for the chart's "shared disease" (potato blight can't infect squash).

Plant with

• Beans^tr — Chart canon, no conflicts — they share a season.
• Corn^P — Afternoon shade and a windbreak in hot spots — and the charts agree.
• Nasturtiums^T — Nasturtium (with marigold) reduced cucumber beetle damage in trials — a research-backed edge for any cucurbit (Minnesota Extension).
• Peas^tr — On the classic charts; peas finish as cucumbers get going.
• Radishes^tr — Also straight off the chart — quick and out of the way.
• Sunflowers^tr — WVU lists them as cucumber companions; just site them so they don't shade the cukes out.

Keep apart from

• Potatoes — A shallow, moderate-feeding cucumber is easily out-competed by a heavy, hilled potato for water and nutrients. Real competition — not the chart's "they give each other blight," which is false.

Plant with

• Beans^P — The stalk is the trellis. Three Sisters, from the corn side — real and free (just don't expect the beans to feed this year's corn).
• Squash & pumpkins^P — Living mulch under the stalks — shades soil, holds moisture, suppresses weeds.
• Cucumbers^tr — On the chart, both rows.
• Peas^tr — Chart canon, cool-season into warm.
• Potatoes^tr — Listed companions on the WVU chart — different families, different pests.

Keep apart from

• Tomatoes — One moth — corn earworm, alias tomato fruitworm — eats both. Don't set a buffet.

Plant with

• Tomatoes^T — The flavor legend is unproven (a 3-year double-blind test found no difference), but basil can cut thrips on tomatoes and modestly lift yield at good density (Minnesota Extension; WVU). Same bed conditions, same kitchen.
• Peppers^tr — Same bed conditions, same kitchen destiny. Thin evidence, zero downside.

Keep apart from

Nothing to dodge. Plant it where you'll actually pick it.

Plant with

• Bush beans^tr — Straight off the WVU strawberry row.
• Spinach^tr — Chart canon, both ways.
• Lettuce^tr — WVU suggests lettuce as a strawberry border.
• Borage^tr — The old herbal pairing on the classic charts. Untested, but harmless.

Keep apart from

The real strawberry rule is rotation, not neighbors: don't plant where tomatoes, potatoes, peppers, or squash grew recently — they share Verticillium wilt.

Plant with

• Corn^tr — The WVU cantaloupe row's pick — a tall windbreak for a sprawling vine.
• Sunflowers^tr — Same row, same canon; site them so they don't shade the vine.
• Nasturtiums^T — A cucurbit like melon shares the squash bug and cucumber beetle — the same pests nasturtium (with marigold) cut in trials (Minnesota Extension).

Keep apart from

• Potatoes — Same story as squash and cucumbers: a sprawling, moderate-feeding vine against a heavy, hilled potato competing for space and nutrients. Competition, not the chart's shared-disease claim.