What is companion planting?

Companion planting is growing certain plants near each other because they help one another — by repelling pests, attracting pollinators, fixing nitrogen, providing shade or improving flavour. The classic example is the three sisters: corn supports climbing beans, which fix nitrogen, while squash shades the soil.

Why should some plants be kept apart?

Antagonist plants compete heavily for the same nutrients, share pests and diseases, or release compounds that inhibit a neighbour's growth. For instance, fennel is allelopathic and suppresses many vegetables, and alliums like onion and garlic stunt beans and peas.

Does companion planting really work?

Some effects are well documented, such as marigold suppressing root-knot nematodes and aromatic herbs masking crops from pest insects. Others are traditional and vary by climate and variety. Treat the pairings as sound starting guidance rather than guaranteed outcomes.

How does spacing relate to companions?

Good companions still need room. The suggested spacing is for the crop itself; pair plants with different root depths or heights so they share a bed without competing, like shallow lettuce beneath taller, deeper-rooted neighbours.

Can flowers be companion plants?

Yes. Marigold, nasturtium and borage are among the most useful companions. They attract beneficial insects and pollinators, act as trap crops for aphids and beetles, or release pest-suppressing root compounds, which is why they appear throughout the chart.

Companion Planting Reference Tool

A productive vegetable bed is partly about which plants sit next to each other. Some pairings deter pests, attract pollinators, or feed their neighbours; others compete and stunt each other. This reference brings together the classic organic companion-planting wisdom into a quick lookup for whatever you are about to sow.

How it works

Pick a crop and the tool shows three things drawn from built-in horticultural data: good companions that benefit it, antagonists to keep apart, and a suggested spacing, along with a short note explaining the mechanism — pest masking, nitrogen fixing, shade, or allelopathy.

The relationships come from well-established traditions and trials, such as:

Tomato + basil + marigold — basil and marigold deter hornworms and whitefly.
Carrot + onion — alliums mask the carrot’s scent from carrot fly.
The three sisters (corn + bean + squash) — beans climb the corn and fix nitrogen while squash shades the soil.
Keep brassicas away from tomatoes and strawberries, and alliums away from beans and peas, because they compete or inhibit growth.

Example

Selecting Tomato lists basil, marigold, carrot, onion and nasturtium as companions, warns against brassicas, fennel and potato, suggests 45–60 cm spacing, and explains that fennel is allelopathic while potatoes share blight.

Notes

Companion effects depend on your climate, soil and varieties, so use these pairings as a planning aid rather than a guarantee. Rotate crops each season to avoid building up soil-borne pests, and observe your own garden — local results are the final word. All data is built into the tool and processed locally in your browser.