Companion Planting Guide

Pick a plant to see what it grows well beside and what to keep it away from. Pairings are the classic, widely-published ones, a mix of tradition and trial, so treat them as guidance for arranging your beds.

About this tool: does companion planting work?

Units Plant

Selected Plant

Intercrop planner

Search for two or more plants to see whether they want the same space at the same time. The cross-section shows what each one occupies above and below ground.

Add a plant

Compress the scale for large plants

Companion planting mixes solid science (trap crops, scent masking, pollinator draws, nitrogen fixing) with garden lore. Use it to arrange beds and rotate families, but your own results and local pests are the final word.

Custom Plants

Custom Plant

Define a plant that isn't in the list. It shows up here and in the Garden Planner with your spacing, color, and companions.

Name

Type

Spacing (in)

Color

Root depth

Mature height (in)

Mature spread (in)

All three are needed for the intercrop planner above, which compares what plants occupy above and below ground. Leave them blank and the plant still works everywhere else.

Companions

Mark which plants it grows well with or should be kept apart from.

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About this tool: does companion planting work?

Evidence

Companions lower pest pressure; they rarely stop it. When a plant does show damage, the Plant Problem Diagnosis Key walks from the symptom to the pest, disease or deficiency behind it.

Companion planting mixes evidenced ecology with folklore on the same chart, and published charts contradict each other. Pairings with a stated mechanism are the ones with support behind them.

Pairings with evidence

Dilution. Pests find a solid block easily and a scattered crop much less so.
Insectary planting. Dill, yarrow and alyssum feed hoverflies and parasitoid wasps, whose larvae eat your aphids.
Trap cropping, if you then deal with the trap crop.
Structure and shade. Three sisters is real engineering, and shade delays bolting.

Using the chart

The reliable version is diversity plus rotation: mix families within a bed, keep something in flower, and move each family on a three or four year cycle. Bad neighbours are usually just competition or a shared pest. Marigolds and legume nitrogen are both weaker than their reputation.

Sources

Notes that say "shown to" are backed by trials; "traditionally" marks pairings no trial supports. Plants per square foot come from the same spacing as the Garden Planner. Full list: sources.