A Companion Spacing Chart for 12 Popular Pairings

Most companion planting charts tell you what pairs with what but leave out the one detail that determines whether the pairing actually does anything: distance. Below are working spacing numbers for 12 common pairings, based on the mechanism behind each one — root contact, scent, shade, or physical support — so you can plant them at a distance where the benefit is real rather than symbolic.

Pairings 1 Through 4: Classic Vegetable Combos

Tomatoes and basil: plant basil within 12 inches of the tomato's base; this distance supports the commonly cited pest-deterrent and flavor-enhancing effect without competing significantly for water, since basil's shallow roots occupy a different soil layer than the tomato's deeper root system. Carrots and onions: alternate at 3 to 4 inches apart in the same row; onion scent masking against carrot fly works best at this tight, evenly distributed spacing rather than in separate blocks. Corn, beans, and squash (three sisters): cluster within a 36-to-48-inch mound, beans at the base of each corn stalk, squash spreading at the mound's outer edge. Cucumbers and dill: within 12 to 15 inches, dill's flowers attract predatory insects that help control cucumber beetles in that immediate radius.

Pairings 5 Through 8: Pest Deterrence and Soil Sharing

Marigolds and tomatoes: 12 to 18 inches, close enough for root-exudate nematode suppression to reach the tomato's root zone. Nasturtiums and squash: 12 to 18 inches, acting as a trap crop for aphids, which cluster on nasturtium leaves before reaching squash. Radishes and carrots: interplant at 3-inch spacing throughout the row; radishes mature and are pulled within 25 to 30 days, before their shallow roots meaningfully compete with the carrot's deeper growth. Peas and spinach: 3 to 4 inches, peas fixing nitrogen that benefits the shallow-rooted spinach nearby, plus peas provide light early-season shade spinach tolerates well.

Pairings 9 Through 12: Height, Shade, and Structure

Lettuce and pole beans: 10 to 15 inches from the bean's base, positioning lettuce within the afternoon shade line without competing directly for root space. Cabbage and dill: 8 to 10 inches, close enough for dill's beneficial-insect attraction to cover cabbage's pest pressure window. Sunflowers and cucumbers: 18 to 24 inches, sunflowers acting as a living trellis for climbing cucumber vines while staying far enough apart that the sunflower's dense root system doesn't outcompete the cucumber for water. Peppers and onions: 10 to 12 inches, onions providing mild pest deterrence through scent without shading the pepper's own light needs.

Reading the Chart in Practice

These 12 ranges cover the pairings gardeners ask about most often, but the underlying logic applies beyond this list: root-based benefits (nitrogen fixing, exudate-based pest deterrence) rarely extend past 18 inches, so keep those pairings tight. Scent-based deterrence can work slightly further out, up to about 2 feet, since it travels through air rather than soil contact. Physical benefits, shade, trellising, wind protection, scale with the taller plant's height and often justify wider spacing, sometimes 18 to 24 inches or more.

A Note on Bed Layout

Fitting several of these pairings into one bed usually means treating each pairing as a small cluster with its own spacing range, then leaving a buffer between clusters equal to roughly the tallest plant's mature spread. A 4-by-8 bed can typically hold 2 to 3 of these companion clusters plus some open row space, depending on which pairings you're combining and how large the tallest plant in each cluster grows.

The Numbers at a Glance

• Twelve widely-used companion pairings each have a specific effective spacing range, not a single "close together" instruction.
• Root-based companion benefits typically hold within 12 to 18 inches; taller-plant shade benefits can extend further.
• Several popular pairings (tomatoes-basil, carrots-onions, corn-beans-squash) can share the same bed section without competing for the same soil depth.
• A pairing planted outside its effective range isn't harmful, it's just decorative rather than functional.
• Printing or saving these numbers avoids re-deriving them from scattered, inconsistent advice each season.

A companion pairing without a distance attached is really just a suggestion. These 12 ranges give you a working starting point grounded in why each pairing helps, so you can plant them close enough to matter without crowding either species out.