What Are the Best Companion Plants for Squash?

Squash — including courgettes, pumpkins, butternut squash, and winter squash — are vigorous, space-hungry plants that spread quickly and suppress weeds naturally with their large leaves. But they have specific needs: their large flowers require dedicated pollinator visits and they are vulnerable to powdery mildew, cucumber beetles, and in some regions squash vine borers. Companion planting addresses several of these challenges at once.

Corn and Beans — the Three Sisters System

Squash is the ground cover component of the Three Sisters polyculture used by indigenous North American farmers for centuries. Corn grows tall, providing structure. Beans climb the corn and fix nitrogen. Squash spreads at ground level — its large, prickly leaves cover the soil surface, suppress weeds, retain moisture, and deter deer and small mammals from approaching the planting. Research has confirmed that corn-bean-squash polycultures produce higher combined yields per unit area than monocultures of any single crop. Timing is critical: plant corn first, add beans when corn is 15–20 cm tall, then squash a week later.

Borage and Nasturtiums to Attract Pollinators

Squash flowers need to be visited by pollinators to set fruit. Male and female flowers are separate on the same plant, and a bee must visit male flowers first before visiting female ones for pollination to occur. Borage and nasturtiums planted around squash beds significantly increase bee activity in the area. Borage in particular attracts bumblebees, which are the most effective squash pollinators because their large body size allows them to access the deep flower. If your courgettes are setting lots of flowers but few fruits, adding borage nearby is the first thing to try.

Dill and Parsley for Predatory Insects

Dill and parsley attract parasitic wasps and predatory beetles when they are in flower. These insects prey on the cucumber beetle and its larvae, which is a significant squash pest in many regions. Allow some of your dill to go to flower in late summer — the flat-topped umbels are extremely attractive to beneficial insects. Position these plants at the sunny end of the squash bed where they will not be shaded by the spreading squash leaves.

Marigolds at the Bed Perimeter

French marigolds planted around the edges of a squash bed deter aphids and nematodes. They also attract hoverflies, whose larvae feed on aphids. Because squash already covers the ground between plants there is limited space for interplanting, so use marigolds as an outer ring rather than trying to mix them in. Tagetes patula (French marigold) rather than African marigold (T. erecta) is the species with the strongest evidence for pest control.

What to Avoid Near Squash

Potatoes and squash should not be grown together — they share several fungal diseases and are both heavy feeders that compete for the same soil nutrients. Fennel is incompatible with squash as it is with most vegetables. Squash planted too close to tall crops like sunflowers can lose so much light that the plants produce only male flowers, preventing fruit set. Give squash room — it will reward you for it.