Companion Planting Chart: What Grows Well Together
Some plants are simply better neighbours. The right companions can confuse pests, attract pollinators, and squeeze more harvest out of the same bed — while the wrong ones compete, share diseases, or stunt each other. This chart distils extension-backed pairings into a quick reference you can plan from.
Pair pest-prone crops with strongly scented companions: tomatoes with basil and French marigolds, carrots with onions, and corn with beans and squash (the classic Three Sisters). Keep onions and garlic away from beans and peas, and keep tomatoes away from corn and potatoes, which share the same pests and diseases.
How companion planting works
Companion planting is not magic — it is applied ecology. University extension trials support four main mechanisms, and the best pairings use at least one of them:
1. Scent masking. Strongly aromatic plants such as onions, garlic, and rosemary can make it harder for pests to find their host crop by smell. This is why carrots and onions are the textbook pair: onion scent confuses the carrot fly, and carrot scent confuses the onion fly.
2. Trap cropping. Some plants are so attractive to a pest that they pull it off your main crop. Nasturtiums lure aphids away from cucumbers and tomatoes; plant them 12–18 inches from the crop you want to protect and check them weekly.
3. Beneficial insect habitat. Flowers such as sweet alyssum, dill, and marigolds feed hoverflies, ladybirds, and parasitic wasps whose larvae eat aphids and caterpillars. A bed with flowers woven through it hosts far more of these helpers than a bed of vegetables alone.
4. Nitrogen sharing. Beans and peas fix nitrogen from the air through root nodules. Grown with hungry crops like corn and squash, they contribute some of that nitrogen to the shared soil — the principle behind the Three Sisters planting.
The companion planting chart
Use this as your planning reference. “Good companions” are pairings with consistent extension support; “avoid” lists pairings with documented downsides.
| Crop | Good companions | Keep apart from |
|---|---|---|
| Tomatoes | Basil, French marigolds, carrots, parsley, nasturtiums | Corn, potatoes, fennel |
| Peppers | Basil, onions, tomatoes, marigolds | Fennel, beans |
| Carrots | Onions, leeks, rosemary, tomatoes, lettuce | Dill, parsnips |
| Onions & garlic | Carrots, tomatoes, lettuce, beets | Beans, peas |
| Bush & pole beans | Corn, squash, carrots, cucumbers, potatoes | Onions, garlic |
| Peas | Carrots, cucumbers, corn, radishes | Onions, garlic |
| Cucumbers | Beans, corn, peas, radishes, nasturtiums | Potatoes, aromatic herbs |
| Lettuce & greens | Carrots, radishes, cucumbers, onions | — |
| Corn | Beans, squash, cucumbers, peas | Tomatoes |
| Squash | Corn, beans, nasturtiums, marigolds | Potatoes |
| Potatoes | Beans, corn, cabbage family | Tomatoes, cucumbers |
| Cabbage family | Dill, onions, nasturtiums, rosemary, beets | Tomatoes, strawberries |
| Basil | Tomatoes, peppers | Rue |
| French marigolds | Almost everything, especially tomatoes | — |
Pairings to avoid (and why)
The “keep apart” column is not folklore — most of these have a concrete reason:
Alliums with legumes. Onions and garlic can suppress the growth of beans and peas. Give these families separate beds or opposite ends of a large bed.
Tomatoes with corn. The corn earworm and the tomato fruitworm are the same insect. Planting them together builds one big buffet for it.
Tomatoes with potatoes. Both are nightshades sharing early and late blight. Keeping them apart — and rotating nightshades on a 3–4 year cycle — slows disease build-up.
Fennel with almost everything. Fennel is allelopathic: its roots release compounds that inhibit many vegetables. Give it a pot of its own.
Dill with carrots. Dill can stunt young carrots, and the two cross-pollinate readily if both go to seed. Let dill flower near cucumbers and brassicas instead, where it attracts beneficial wasps.
Using the chart in a small bed
Companions do not override spacing — every crop still needs its recommended room. Here is how the chart looks in a single 4×8-foot bed, arranged north to south so nothing shades its neighbours:
North row (trellis): cucumbers climbing a trellis, with nasturtiums sown at its base as a trap crop. Centre rows: tomatoes staked every 24 inches, basil tucked between each pair, French marigolds dotted along the row ends. South rows: carrots and onions in alternating rows 6 inches apart, with lettuce filling the sunniest edge.
Every pairing in that plan appears in the chart above, and every crop still gets its full spacing. That is the whole method: choose companions first, then give each plant its normal elbow room.
Turn pairings into a planting plan
Knowing what grows well together is half the plan — the other half is timing. Work out your indoor sowing and transplant dates from your last frost date.
Frequently asked questions
Does companion planting really work?
Parts of it have solid evidence: trap cropping with nasturtiums, nematode suppression by French marigolds planted densely for a full season, and nitrogen contribution from legumes are all extension-documented. Scent masking is plausible but harder to prove. Treat companions as a helpful layer on top of good spacing, soil, and watering — not a substitute for them.
What is the Three Sisters planting?
It is the Indigenous American method of growing corn, beans, and squash together: corn provides a trellis, beans fix nitrogen, and squash shades the soil. Sow corn in a block rather than a single row, wait until it is about 6 inches tall, then sow beans at the base of each stalk and squash in the spaces between hills.
Can I plant tomatoes and peppers together?
Yes. Both are nightshades with similar needs for sun, warmth, and fertility, and neither appears on the other’s avoid list. Just remember they share diseases, so rotate the two together on a 3–4 year cycle away from the spot where potatoes grew.
What should not be planted next to garlic?
Beans and peas. Garlic and onions can suppress legume growth, so keep them in separate beds or at opposite ends of a large bed.
Do marigolds really repel pests?
French marigolds (Tagetes patula) are the type with evidence: grown densely for a full season, they suppress root-knot nematodes. Their scent may also confuse some flying pests, but they are not a force field — combine them with row covers and handpicking for reliable control.
Related guides
Easiest Vegetables to Grow for Beginners
Start with forgiving crops, then pair them up using the chart above.
How to Grow Tomatoes in a Raised Bed
Tomatoes anchor most companion plans — here is how to grow them well.
How Often Should I Water My Vegetable Garden?
Good neighbours still need the right amount of water.
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