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Nasturtiums are so more than beautiful summer flowers. These trailing plants hold a lot of benefits in the vegetable garden, too.
Last year I grew nasturtiums in my raised beds, and I’ve never seen so many aphids drawn to a single plant! I was disappointed until I realized that’s just one reason that gardeners grow nasturtiums – to divert pests away from their more valuable crops.
Nasturtiums make excellent companion plants for a number of vegetables due to their insect-attracting and pest-repelling properties. Nasturtiums serve as a trap crop for some pests – aphids in particular – but the fragrant flowers also attract beneficial insects that keep bad bugs under control.
Some growers have reason to believe that Nasturtiums may also repel other pests like cucumber beetles and squash, but there’s more evidence to suggest that nasturtiums draw pests away from other crops. Read on to learn more about how to grow nasturtiums as companion plants in your vegetable garden.
One of the easiest annual flowers to grow, nasturtiums deserve to hold space in everyone’s garden. While the succulent stems aren’t great for cut flowers, nasturtium flowers are edible and add a peppery flavor to salads. Nasturtium buds are also lovely garnishes for soups and even drinks.
Nasturtiums come in two types–Tropaeolum major, which has a trailing growth habit, and Tropaeolum minor, a more compact plant with lateral bushy growth. In the garden, trailing nasturtiums add elegance to any wall or fence. Compact nasturtiums are more often grown as companion plants, but even these varieties still have an exquisite look about them, planted in containers or raised beds and allowed to spill over the sides.
Wait to direct sow nasturtium seeds or transplant seedlings until after all danger of frost has passed, usually one or two weeks after the last average frost date, when the soil has warmed up to between 55℉ and 65℉.
Nasturtiums aren’t picky about soil type – so long as the soil drains well, nasturtiums will thrive. These drought-tolerant plants actually prefer poor to average soil, making the bushy and vining plants the perfect choice from groundcover.
Nasturtiums don’t need fertilizer – the extra nutrients will result in fuller plants but fewer flowers. Grow nasturtiums in the field or in containers, the plants aren’t picky – so long as they receive at least six hours of direct sunlight they will thrive and work their magic in the garden!
A word on invasiveness
As lovely as trailing nasturtiums are, they are known to take over whatever growing space they can, insofar as choking out other plants. Even dwarf varieties have a tendency to sprawl, so keep your nasturtiums contained in a bed or planter, or if in the field, pull the plants up by the roots at the end of the season to slow their spread. Remove old flowers before they set seed–this will keep your garden looking fresh and will prevent nasturtiums from self-seeding.
Nasturtiums for pest control
Nasturtiums have long been used as a biological pest management tool in the garden. Folk gardening knowledge claims that nasturtiums have some pest-repellent properties, but it’s more likely that nasturtiums confuse pests or divert pests away from other crops, potentially evading worse invasions.
Planting nasturtiums as a trap crop
Many gardeners have had success using nasturtiums as a kind of sacrificial planting. In theory, a mass planting of mature nasturtiums will seem more desirable to pests than immature transplants–meaning that the pests will forgo your other crops for the nasturtiums. This method of planting, called trap cropping, has been proven as an effective integrated pest management strategy.
Start your trap crop nasturtiums early, and transplant them out a few weeks earlier than your other crops so the trap crop will mature before the rest of your garden. If possible, plant your nasturtiums in a block several rows deep, so that they’re more noticeable to insects. The University of Georgia recommends locating your trap crop between eight and twelve feet from the rest of your garden.¹
Other plants can be grown as a trap crop, but nasturtiums are particularly effective and have the added benefit of being easy to grow. It seems that aphids and cabbage moths are especially drawn to yellow nasturtiums, so go with varieties like Orange Gleam for the best results.
Of course, trap cropping really only works for those gardeners who have enough growing space to justify two separate gardens. For growers working in smaller spaces, interplanting nasturtiums with other plants can also prove very effective at managing pests.
Using nasturtiums as border plants
Lining your garden with a barrier of nasturtiums is another way to creatively manage pests in the garden without resorting to sprays. Nasturtiums can act as the first line of defense by attracting insects and slowing their progress into other parts of your garden.
Nasturtium borders are particularly helpful in controlling aphids (and the ants that farm the aphids) To be effective, plant your nasturtium border about two feet from your other crops.
Attracting beneficial insects with nasturtiums
Bold and fragrant nasturtium blooms attract a host of beneficial insects and pollinators. Predatory insects like green lacewings and hoverflies flock to the nectar-rich flowers, as do bees and butterflies.
Pollinators are an essential part of a healthy garden ecosystem. Pollinators are what allow our favorite vegetables like cucumbers and beans to produce fruit. Intercropping nasturtiums with vegetables promotes pollinator traffic within the garden, improving the flavor of the yield and making the harvests that much more abundant.
Ladybugs are attracted to the aphids that seem to take up residence on nasturtium plants. Adult green lacewing and hoverflies visit nasturtiums to feed on pollen and nectar and linger long enough to lay eggs by aphids and other pests. Their eggs hatch and the larvae devour soft-bodied insects like aphids and thrips.
Parasitic wasps are also drawn to nasturtiums to feed on the sweet-smelling flowers. Parasitic wasps lay their eggs inside other insects like caterpillars, as well as beetle and fly larvae. The eggs hatch inside the host eating the unfortunate insect alive from the inside.
Nasturtiums as companion plants
While nasturtiums are used to attract and divert a few pests, these plants may actually repel some other common garden pests like cucumber beetles and cabbage loopers. Nasturtiums are known to emit a chemical toxic to some insects.
Intercropping nasturtiums with vegetables
Interplanting nasturtiums with your other crops shields the pest-susceptible plants from feeling the full force of the invasion. Plant nasturtium as companions anywhere in your vegetable garden where you have an empty hole, or in a garden bed at least a foot away from other plants.
Trailing nasturtiums will happily climb tomato and cucumber trellises, and bushy nasturtiums fit perfectly, tucked into the eggplant or squash beds.
Best vining varieties
Plant vining nasturtiums on the same trellis as tomatoes and cucumbers to repel cucumber beetles, whiteflies, and squash bugs.
A trailing variety that reaches six feet in length, Moonlight boasts lovely cream-colored flowers. Buy Moonlight nasturtium seeds from Swallowtail Garden seeds.
- Amazon Jewel
Another trailing variety reaching six feet long when fully mature, Amazon Jewel is the perfect blend of warm-toned flowers atop variegated foliage. Order Amazon Jewel nasturtium seeds from Renee’s Garden.
Best compact varieties
Try growing compact nasturtium varieties next to bushy plants like eggplant, potatoes, and beans for a little extra protection from cucumber beetles, Colorado potato beetles, and the Mexican bean beetle.
- Alaska Mix
A fun mix of flowers with a controlled growth habit, the Alaska Mix is an excellent choice for pest control. Pollinators love the brightly colored blooms ranging in color from gold to orange to scarlet. Alaska Mix seeds are available for purchase from Eden Brothers Seed Company.
- Empress of India
This compact plant produces the most beautiful ruby-colored funnel-shaped flowers. This heirloom variety is prized for its rich color and resistance to disease. Get your Empress of India nasturtium seeds from West Coast Seeds.
Nothing is going to be quite as effective at controlling garden pests as a chemical spray, but for the gardener looking to manage pest invasions organically, incorporating nasturtiums into the vegetable garden is a good starting point.
The easy-to-grow annual flowers are as beautiful as they are purposeful–nasturtiums may repel some pests, and their colorful flowers certainly attract beneficial insects. At the very least, nasturtiums don’t seem to have a negative impact on the garden, so why not give the annual flowers a trail run in your garden this season, just to see if pests don’t seem a little more scarce?
¹ Trap Cropping for Small-Market Vegetable Growers | UGA Cooperative Extension.” UGA Extension, 27 September 2017, https://extension.uga.edu/publications/detail.html?number=C1118&title=Trap%20Cropping%20for%20Small-Market%20Vegetable%20Growers. Accessed 1 May 2022.