Tomato Companion Plants — What Grows Well With Tomatoes

Basil (traditional): The classic pairing: basil's scent may confuse some flying pests, and the two share water and sun needs so they thrive in the same bed. Claims that basil improves tomato flavor are folklore.

Marigold (documented): French marigolds (Tagetes patula) suppress root-knot nematodes in soil — one of the few companion effects with solid research behind it. The effect works through root exudates, strongest when marigolds grow in the spot beforehand.

Onions (traditional): Alliums' strong scent is traditionally credited with deterring aphids and some beetles, and onions occupy little root or air space, so there's no competition cost either way.

Garlic (traditional): Like onions: compact, non-competing, and traditionally credited with deterring spider mites and aphids. Fall-planted garlic is harvested mid-summer, freeing space just as tomatoes peak.

Lettuce (traditional): Lettuce bolts in summer heat — tomato plants cast exactly the afternoon shade that keeps it going longer, and shallow lettuce roots don't compete.

Spinach (traditional): Same logic as lettuce: a cool-season understory crop that benefits from tomato shade and finishes before the tomato needs the space.