Even though there are no clear guidelines for watermelon companion planting, there are still a few things to consider when selecting where to plant watermelons, and which plants to put next to them. Some companion plants for watermelons can reduce pest infestations, like garlic, radishes, corn, broccoli, marigolds, and certain herbs. Lavender and borage can help promote pollination, while pole or bush beans can increase nitrogen in the soil. It’s important to avoid planting certain species near watermelons, which can attract pests. Here are the best and worst companion plants for watermelons:
Size and Light Considerations
Unless you are growing a bush-type watermelon, the plants need a lot of space. Their vines can reach 20 feet in length. The spread is not connected to the size of the fruit—both the small variety Sugar Baby and large one Crimson Sweet have a spread of 10 to 12 feet. Also, watermelons require full sun so they should not be planted next to any tall crops that can cast shade on them. Taking those two requirements—space and sunlight—into consideration will already narrow down the possible spots in your garden that are suitable for growing watermelons. One of the best steps for prolific watermelon growth is crop rotation.
Best Companion Plants for Deterring Pests
The two main pests that affect watermelons are aphids and cucumber beetles. Not only do these insects feed on the plants but they can also transmit viruses from plant to plant, which is often more damaging than the insect’s feeding. There are many different aphid species. The one that attacks watermelon is the melon or cotton aphid (Aphis gossypii). The following plants can either deter the aphids or can serve as trap plants to distract the aphids from attacking the watermelon plants:
Garlic Catnip Dill Mint Nasturtiums
Cucumber beetles, both the spotted cucumber beetle and the striped cucumber beetle, feed on watermelons. The striped cucumber beetle can also transmit bacterial wilt, a deadly plant virus. The suggested crops to keep cucumber beetles under control include:
Corn Broccoli Radishes Nasturtiums Marigolds Tansies
Worst Companion Plants
Because other members of the Cucurbitae family are all attacked by cucumber beetles, planting watermelons next to these crops is not recommended:
Cucumbers Summer squash/zucchini Pumpkins Winter squash
Potatoes can attract different aphid species, including the melon aphid, so avoid planting potatoes next to watermelons. While tomatoes and peppers are not attacked by the same aphid species as watermelons, planting them next to each other is not recommended because it can lead to space issues. Keep in mind that the lack of good air circulation in a densely planted garden plot can accelerate plant diseases, especially in plants with dense foliage, such as tomatoes. Avoid members of the aster or sunflower family and roses. They attract the highest number of aphid species that may harm watermelons.
Best Companion Plants for Pollination
Watermelons have both male and female flowers on the same plant. The pollen is quite sticky and requires insects, mostly bees, to move it from the male to the female flowers for fertilization and fruit production. Seedless (triploid) watermelon varieties need seeded (diploid) watermelons and the bees they attract nearby to pollinate the flowers of the seedless watermelons. Whichever type of watermelon you grow, it is crucial to attract bees to your garden. Marigold, lavender, and borage are good companion plants for watermelons because of their continuous or intermittent blooming. Flowers of highly hybridized cultivars are generally less attractive to pollinators than heirloom varieties. Seeding a strip of mixed wildflowers next to your garden is also a good way to attract native bees, which are just as important as honeybees for watermelon pollination. Again, bear in mind the mature size of the watermelon vines, as well as the size of the melons, to make sure the flowers or flowering herbs intended to attract pollinators aren’t being overgrown or crushed.
Best Companion Plants for Nutrients
Because pole or bush beans enrich the soil by fixing nitrogen, they are generally viewed as good companion plants for watermelons. But there is one caveat especially with pole beans—they should not be casting much shade on the watermelons. Place your bean teepee or trellis accordingly, facing it north or east, so it does not obstruct the midday and afternoon sun that your watermelons need to thrive.
