Does companion planting really work?

Many combinations are well-documented: alliums deter carrot fly, marigolds repel nematodes, and the Three Sisters (corn, beans, squash) is a proven system used for centuries. At worst it increases biodiversity.

How close should companion plants be?

Close enough to benefit each other but not competing for light, water or nutrients. Generally 15-30 cm between different species, following each crop recommended spacing.

What is the Three Sisters planting method?

An ancient method: sweetcorn provides support for climbing beans, beans fix nitrogen in the soil, and squash shades the ground reducing weeds. Plant in blocks rather than rows for best results.

Companion Planting Layout Calculator — Free Planting Tool

Companion Planting Layout Calculator

Calculate companion planting layout and spacing for common vegetable combos.

Main CropThe lead vegetable; companions and spacing are looked up from RHS grow-your-own figures for this crop.

Bed Length

The long side of the bed, along which plants sit in each row. A standard raised bed is 2.4–3 m.

Bed Width

The short side, across which rows run. Keep to 1.2 m so the centre is reachable from both sides without treading on soil.

How We Calculate This

Select your main crop and enter your bed dimensions. The calculator looks up recommended companions and crops to avoid, then estimates plant counts from each species' optimal spacing.

Rows run across the bed width at the row spacing (pitch) you set; plants per row are spaced along the bed length at the crop's own spacing (both use the fencepost rule: plants = length ÷ spacing + 1). Companions are counted as interplanted accents — set between the main plants and at row ends — so they stay roughly equal to or fewer than the main crop rather than forming a second full crop. An edge buffer keeps plants away from the bed edges for access and airflow.

Frequently Asked Questions

Last updated: March 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.