Watermelon Companion Plants | Best and Worst

This sweet and refreshing fruit is 92% water, as suggested by its name. Watermelons (Citrullus lanatus) are the epitome of summer and can be eaten alone or used in a variety of beverages and dishes. 

Watermelons are notoriously easy to grow so long as you fulfill their environmental needs and care requirements. They have a long growing season so require a bit of patience, but the juicy fruit reward is definitely worth it. 

Although they do well on their own, selecting watermelon companion plants can improve their overall health and growth and they are very compatible with lots of other crops, so you’ll have a lot of partner options to choose from. 

That being said, there are some plants that you should avoid growing with watermelons as they can cause damage. Deciphering which plants to pick and which to avoid can be challenging. That’s why I have done all the hard work for you.

In this article, I provide a list of plants that make good and bad watermelon companions and why, to help you pick the perfect partner. 

Companion Planting Explained 

Companion planting is a form of polyculture and is opposite to monocultures that a lot of agricultural industries use. This technique involves growing different plant species close together. This reflects the natural environment and supports our ecosystems and wildlife.

The idea behind companion planting is to utilize the natural advantages that different plants have to offer and combine them in such a way that they obtain mutual benefits from one another. 

This ancient practice was traditionally used to grow crop plants, with the aim of increasing their yield in a natural and organic way. Companion planting has proved to be highly successful and is now used in a variety of settings, from agricultural to landscaping to ornamental. 

A famous example of companion planting was developed to grow beans, sweetcorn and squash and is known as the “Three Sisters” method. 

Beans increase the nitrogen content of the soil, aiding the growth of the sweetcorn and squash. The tall sweetcorn provides the beans with a sturdy structure to climb up. The large squash leaves shade the soil which keeps it moist and suppresses the growth of weeds. 

Benefits

Companion planting results in a variety of natural benefits that aid the grower and the wider environment. Some of the most common benefits of companion planting include: 

Attract Beneficial Insects: Plants with vibrant or highly fragranced flowers are generally most attractive to pollinators. Since most of the worlds crop plants are pollinated by animals, it’s beneficial to plant pollinator attracting plant near your crops. Bees, butterflies and birds and some of the most common pollinators.

Certain plants attract predatory insects, such as wasps or ladybugs. These predators will prey on pests like aphids, slugs or flies, preventing them from damaging your crop. 

Saves Space: Watermelons specifically require a lot of growing space. Not only are the fruits themselves large, but their vines and roots are extensive. Companion planting helps to fill any empty patches of soil, maximizing the growing space. 

Improves Soil Health: Some plants are able to improve the nutrient content of the soil. Watermelons are heavy feeders and require large amounts of nitrogen specifically. Legumes are able to convert atmospheric nitrogen into a fixed form in the soil, increasing the nitrogen supply for neighboring plants. 

Pest Control: Certain plants release scents or chemicals that act as natural insect repellents, eliminating the need to use chemical-based pesticides. The fragrance of certain companions can be used to mask the scent of the crop you are trying to protect. 

Other companions can be used as “trap crops” by being more attractive to pests than your crop plant, luring them away from it.

Provides Structural Support: Strong and tall companions can act as natural support structure for vining plants to cling to and climb up. Some smaller varieties of watermelon may benefit from having a vertical support to grow up.

Suppresses Weeds: Watermelons have dense foliage that is low-lying and far-reaching. As such, watermelons can act as “smother crops” to suppress the growth of weeds that would compete with your plants for resources. The foliage also helps to keep the soil cool and moist. 

Considerations

Although there are a lot of good companions for watermelons, there are some plants that should be avoided. Consider the compatibility of different species, and also the benefits you wish to receive from them. 

Environmental requirements are a major factor with regard to compatibility. A plant that needs alkaline soil to grow would be a bad companion to one that needs acidic soil to flourish. 

Eradicating pests and diseases is especially important with crop plants as they can greatly damage the yield. Avoid planting species together that are vulnerable to the same pests and diseases, as this will make it easy for them to spread among your plants.

Think about the behavior of the plants, both above and below the soil. For example, pairing a shallow-rooted plant with a deep-rooted one is a great way to use the growing space and reduce competition between the roots for nutrients and water.  

Best Watermelon Companion Plants

Watermelons grow best in loose, sandy soil that drains well. Although they require lots of water to produce round, juicy fruits, they dislike saturated soil. Ideally, the soil should be slightly acidic with a pH between 6.0 and 6.5. As watermelons have a deep root system, they require deep soil to grow.

Being native to Africa, watermelons thrive in tropical to temperate climates. They grow best in temperatures between 70oF and 90oF. Watermelons require at least 8 hours of direct sunlight every day in order to produce flowers and fruit.

Watermelons cannot tolerate frosts or cold temperatures. They are hardy across USDA zones 2 through 11. 

The companions I have recommended thrive under the same conditions and induce a variety of benefits, ranging from pest control to encouraging pollinators. Great companions for your watermelons include: 

Herbs

Oregano: This fragrant herb is an excellent addition to many culinary dishes. Its strong scent keeps harmful pests away from watermelons whilst attracting pollinators. 

Mint: The fresh scent of mint acts as a natural pest repellant. Mint also improves the taste of watermelons when grown together. 

Catnip: The scent catnip produces wards off pests from your watermelons and also enhances their flavor. 

Fruits and Vegetables 

Beans: Watermelons have very high nitrogen requirements. Beans have nitrogen-fixing bacteria in their root nodules which increases the nitrogen content of the soil. 

Garlic: The pungent smell of garlic is great at repelling pests including aphids and rodents that can damage your watermelon. Garlic grows well in acidic soil and full sunlight, just like watermelons. They also offer anti-fungal benefits, making it a great companion plant option. 

Carrots: These vegetables can be intermittently planted between your watermelons to fill in the gaps. They grow much longer than they do wide, so won’t interfere with the watermelons growing space. 

Sweetcorn: The tall stalks of sweetcorn provide a structure for small, vining watermelons to climb up. Just be careful the corn won’t shade the watermelons. 

Lettuce: This fast-growing vegetable is great at suppressing the growth of weeds that would otherwise be in competition with your plants for resources. It also has shallow roots that won’t interfere with the watermelon’s roots. 

Radishes: Radishes are a rapidly growing vegetable. They deter a number of pests, including cucumber beetles. Radishes are also great for stifling the growth of weeds. 

Maize: This cereal crop is a worldwide staple. Maize and watermelon suffer from different pests and diseases so make good companions. 

Flowering Annuals and Perennials 

Nasturtiums: These peppery, edible flowers make a pretty garnish for many dishes. The delicate flowers add colour and produce a sweet scent that attracts many pollinators to your garden. Nasturtiums make a great trap crop to keep pests away from your watermelons. 

Marigolds: These flowers make excellent companions for many plants. Their fiery colored flowers create a contrasting coloration with the predominantly green watermelon patch. Pollinators are attracted to the blooms and fragrances of marigolds, aiding the pollination of your watermelons. 

Bad Companion Plants for Watermelon

Here is a list of plants you should keep well away from your watermelons: 

Cucumbers: Watermelons and cucumbers suffer from the same pests and are especially susceptible to cucumber beetles.

Zucchinis: Watermelons and zucchinis are vulnerable to the same pests and have similar nutrient requirements, so will be in competition for them.  

Potatoes: Potatoes may attract pests and introduce blight to your garden.

Tomatoes: Tomato plants grow tall and bushy so run the risk of shading out your watermelon. 

Pumpkins: Like watermelons, pumpkins grow large and are heavy feeders if planted together, both crops are likely to be in competition for space and nutrients. 

Citations

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Ben's horticultural interest grew when graduating from Hertfordshire University in 1997. Having contributed to numerous publications including Better Homes & Gardens, Garden Design Magazine, and The English Garden. He is also the author of Propagating Houseplants Made Easy.