Companion Planting Chart for Small Gardens

Companion planting attracts a lot of folklore. Some of it holds up in trials; some is Victorian invention repeated until it sounded like fact. This chart sticks to pairings with a plausible mechanism and a real benefit in a bed of two square metres or less.

What Companion Planting Can and Cannot Do

Four mechanisms do most of the honest work.

• Physical structure. Tall plants shade or support shorter ones. Sweetcorn holds beans; lettuce sits under tomatoes and stays cool.
• Habitat for predators. Umbellifers and small daisies feed hoverflies and parasitic wasps, whose larvae eat aphids in quantity.
• Host disruption. Strong scents make it harder for a pest to find its host. Interplanting carrots with onions genuinely reduces carrot fly damage.
• Trap cropping. A more attractive sacrificial plant pulls pests off the crop you care about. Nasturtiums do this for blackfly.

What it does not do is replace the basics. It will not rescue a plant short of light, cramped or unfed, will not stop blight, and will not make a poor bed fertile. Treat it as a 10-20% improvement on top of good growing.

The Small-Garden Companion Chart

Combinations Worth Avoiding

The keep-apart column matters more than the good-companion column, because a bad pairing in a small bed costs real yield.

Fennel is the extreme case. It releases compounds that inhibit germination and growth in most vegetables. Grow it in its own container, away from everything.

Alliums and legumes genuinely do not get on. Onions, garlic, leeks and chives measurably stunt beans and peas. In a 2 m bed, keep at least 40 cm between them.

Tomatoes and potatoes share late blight and several viruses, so one infection takes both. And the failure mode nobody labels: mismatched water needs. Rosemary next to basil kills one of them. In shared pots, match water and feeding before you worry about pest theory.

Flowers That Earn Their Space

In a small garden every plant needs to justify its footprint. These four do.

• French marigold (Tagetes patula). The most evidence-backed of the lot. Root exudates suppress root knot nematodes and the foliage deters whitefly. Plant three per square metre.
• Nasturtium. A trap crop that works almost too well — blackfly will cover it and leave your beans alone. Site it 50 cm away, not in the middle. Leaves and flowers are edible and peppery.
• Borage. A pollinator magnet that flowers for months, superb next to courgettes and strawberries. It self-seeds enthusiastically, so deadhead.
• Calendula. Feeds hoverflies whose larvae eat aphids in serious numbers, and is happy in a 5 L pot on the edge of a bed.

How to Use the Chart in a Two-Metre Bed

Do not try to satisfy every row. In a small space, apply it in this order.

1. Place your tallest, hungriest crop first, on the sunniest side, and check it against how much sun vegetables really need.
2. Fill the shaded strip behind or below it with lettuce, spinach or chard.
3. Add one alliums-and-carrots pairing if carrot fly is a problem where you are.
4. Reserve about 10% of the bed for flowers, sited at the edges rather than the centre.
5. Keep every avoid-pairing at least 40 cm apart, or in separate containers.
6. Rotate families each season so the soil does not carry pests over.

For container growers the chart applies per pot, and pot volume is usually the binding constraint on what can share.

One good pairing you actually plant beats a perfect chart you never use.

Working all this out on graph paper takes a while. Vegarden lays out your bed, flags pairings that clash and keeps the rotation straight from season to season.