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Companion planting has been around for generations, but most of the plant partnerships recommended have little basis in actual science. Times are changing though, thanks to an abundance of current research looking at the benefits of partnering certain plants together. My most recent book, Plant Partners: Science-based Companion Planting Strategies for the Vegetable Garden (Storey Publishing, 2020), presents effective interplanting strategies home gardeners can use to grow a better garden. In a prior article, I’ve examined the best companion plants for tomatoes, but in this article, let’s take a look at science-backed zucchini companion plants for the vegetable garden.
A quick look at modern companion planting
Today’s companion planting strategies are backed by current and ongoing research at university and agricultural research facilities throughout the world, rather than being based on old wives’ tales and folklore. In my book, you’ll find an extensive reference list of these studies, along with dozens of useful plant partnerships throughout the pages. This modern take on companion planting is called interplanting or intercropping, but regardless of the name used, it involves combining plants together for a specific benefit.
The partner crops can be planted closely together at the same time, or they can be grown in succession – one after the other – to gain the desired benefits. In all cases, however, companion planting is about growing a polyculture where different species of plants thrive together in a diverse, more stable, environment.
The benefits of zucchini companion plants
Partnering your zucchini plants with other plant species results in several possible benefits, including disease suppression, improved soil health, weed suppression, pest control, and enhanced pollination, depending on the partner plant selected. Let’s take a look at some specific, well-studied zucchini companion plants and how you can use them to help you grow a better garden.
Zucchini companion plants for pest control
1. Blue Hubbard squash:
If you grow squash, you’ve probably experienced problems with squash bugs and squash vine borers. One of the best zucchini companion planting methods for deterring these two common pests involves planting a trap crop of blue Hubbard squash. Both squash bugs and squash vine borers prefer blue Hubbard to other varieties of summer and winter squash, including zucchini. The blue Hubbard plants serve as a sacrificial trap crop, drawing these pests away from your zucchini crop and limiting damage. Plus, blue Hubbard squash are far more tolerant of these pests than other squash types, so even if they are used primarily to lure pests, you’ll still likely be able to make a harvest. Be sure to plant the blue Hubbard plants three to four weeks prior to planting your zucchini and locate them on the periphery of the vegetable garden, several feet away from your zucchini.
One zucchini companion plant that’s both beautiful and useful is the nasturtium. Gardeners who battle squash bug infestations are wise to interplant their zucchini plants with trailing nasturtiums. A significant decrease in the number of squash bugs and squash bug damage was found when these two plants were combined. Nasturtiums produce lovely edible flowers and can also potentially boost pollinator numbers in the squash patch.
Companion plants to increase pest predation in the zucchini patch
3. Small-flowered herbs:
Zucchini plants fall prey to several different pests, including aphids, whiteflies, spider mites, and others. Young plants are especially vulnerable. Thankfully, there are many species of beneficial insects that readily make a meal out of these common pests. By companion planting your zucchini crop with small-flowered herbs such as oregano, dill, fennel, and thyme, you’ll be providing nectar and pollen for tiny parasitic wasps, ladybugs, lacewings, and other predators of these garden pests. Surround your zucchini plants with flowering herbs each season or edge your raised beds with them. Just remember to stop harvesting the herbs by early summer so they have enough time to bloom and produce nectar.
Zucchini companion plants for soil health
4. Small white clover:
Nitrogen-fixing cover crops, including legumes like white clover, are excellent zucchini companion plants whether they are grown side by size or in succession with your zucchini crop. The nitrogen added to the soil by the small white clover helps feed the zucchini plants. Just be sure to mow the clover before it drops seed to keep it from becoming “weedy.”
Zucchini plant partners for improved pollination
Yes, other types of squash are great companion plants for zucchini, particularly when it comes to improving pollination rates. You see, squash plants are often pollinated by a specialized family of bees called squash bees (Peponapis species). There are about 13 North American species in this family, with P. pruniosa being the most common. These beautiful little native bees are specialists who pollinate members of the squash family exclusively, though other bees will do the job, too. Since these bees are so highly specialized, they can only nectar on members of the squash family. This means if you want more of them around, you need to plant as many members of the squash family as you can. Add melons, cucumbers, pumpkins, gourds, and both summer and winter squashes to your garden.
The best zucchini companion plants to reduce weeds
6. Medium Red Clover:
Companion planting techniques focused on weed reduction sometimes involve the use of living mulches. Living mulches are plants grown around and between rows of the desirable crop. In the case of both winter squashes and summer squashes like zucchini, the best way to control weeds is by interplanting with a living mulch of medium red clover (Trifolium pratense). This legume smothers weeds and helps break up heavy soil. And, like other legumes, it fixes nitrogen and provides it to nearby plants in both a living state and when the clover plants are left to decompose in the soil. Additionally, when grown as a weed-suppressing living mulch, medium red clover also provides habitat for pest-eating beneficial insects and pollinators. In studies, the best results were achieved by alternating strips of clover with rows of squash. Keep the clover mowed regularly, especially before it develops seed.
Field oats (Avena sativa) make an inexpensive and reliable living mulch for weed control around zucchini and other taller vegetables like tomatoes, peppers, and eggplants. They grow quickly during the summer and autumn but are easily killed by cold winter temperatures. The key to growing oats as a zucchini companion plant is regularly mowing the oats throughout the growing season. Leave the mowed oat stems in place, and they will further act to suppress weeds. Because oats are allelopathic (meaning they contain compounds that inhibit the growth of certain nearby plants), it’s important to only partner them with vegetables grown from transplants, not from seed. Always plant your zucchini companions as young transplants when partnering them with oats.
8. Yellow mustard:
Field mustard (Sinapis alba) is an annual cover crop. When used as a living mulch, it has been shown to increase the yields of zucchini and other types of summer squash. The same study also noted that this plant pairing decreased the density of certain pests and diseases, such as aphids and whiteflies. A cover crop of mustard around your zucchini crop restricts weed seed germination. Mustard is winter killed at about 25 degrees F. The powerful root system of this zucchini companion plant breaks up compacted soils, too. Always mow mustard plants down before the seeds develop to keep them from taking over the garden.
By incorporating these zucchini companion plants into your garden, you’ll discover many potential benefits. Don’t be afraid to experiment. Keep records and try new combinations each season to find what works best for you and your garden.
For more science-based companion planting tips for the vegetable garden, please check out my book, Plant Partners.
For more on growing healthy vegetables, please visit the following articles:
– Zucchini growing problems
– Cucumber growing problems
– Tomato diseases and their organic controls
– Managing plant diseases
– The best tomato companion plants