Nasturtiums are versatile annual plants, increasingly recognized for their role in companion planting. This practice involves growing different plant species together to create a mutually beneficial environment that enhances garden health and productivity.
Benefits of Nasturtiums in Companion Planting
Nasturtiums offer several advantages in garden design. Their strong, peppery scent deters common garden pests, including squash bugs, cucumber beetles, whiteflies, and various caterpillars, protecting nearby susceptible crops.
Beyond deterring pests, nasturtiums serve as an effective “trap crop” for aphids. They attract these insects away from more valuable vegetable plants. Gardeners can then manage the aphid population on the nasturtiums, either by removing heavily infested plants or treating them, reducing overall aphid pressure in the garden.
Nasturtium flowers attract beneficial insects. Their bright, nectar-filled blooms draw in pollinators like bees, butterflies, and hummingbirds, essential for fruit and vegetable production. They also attract predatory insects such as ladybugs, lacewings, and hoverflies, which prey on aphids and other pests.
Nasturtiums’ vigorous growth makes them excellent living ground cover. Their dense foliage suppresses weed growth by blocking sunlight and retains soil moisture by shading the surface. While not a primary soil improver, they offer a minor soil benefit upon decomposition.
Ideal Companion Plants for Nasturtiums
Nasturtiums benefit various garden plants. They are particularly effective near Brassicas (cabbage, broccoli, kale), protecting them by deterring aphids, whiteflies, and cabbage worms through scent or as a trap crop.
Cucurbits, including squash, zucchini, and cucumbers, also benefit. Nasturtiums repel squash bugs and cucumber beetles, reducing pest populations near these vining plants.
Tomatoes thrive alongside nasturtiums. Nasturtiums deter whiteflies, attract pollinators benefiting fruit set, and lure aphids away, acting as a sacrificial plant.
Nasturtiums planted at the base of fruit trees, such as apple and peach trees, act as ground cover, retaining soil moisture and suppressing weeds. They also deter codling moths and attract beneficial insects that prey on fruit tree pests.
Radishes benefit as nasturtiums act as a trap crop for flea beetles, drawing them away. For beans, nasturtiums deter Mexican bean beetles.
Plants to Avoid Near Nasturtiums
While largely beneficial, some plants compete negatively with nasturtiums. Those with similar nutrient requirements or growth habits, like leafy greens and smaller brassicas, may struggle if planted too closely, as nasturtiums compete for resources and sunlight.
If nasturtiums are primarily used as a trap crop for aphids, planting them directly adjacent to highly susceptible plants like brassicas can be counterproductive without careful management. Aphids might move to the main crop if the trap crop becomes too infested or is not properly maintained. Strategic placement with some distance is more effective for pest management.
Fennel is a poor companion, as it can release chemicals that inhibit the growth of nearby plants. Mint, with its aggressive spreading root system, can outcompete nasturtiums for space and nutrients. Potatoes are also not ideal companions, as both plants can attract similar pests, potentially exacerbating problems.
Tips for Effective Nasturtium Companion Planting
Strategic placement is important for maximizing nasturtium benefits. For pest deterrence, plant them as a border around vegetable beds or intersperse them among rows of susceptible crops. When using them as a trap crop, positioning them about five to six feet away from the main crops can be effective, preventing pests from easily migrating once the nasturtiums are infested.
Regular monitoring of nasturtiums is important, particularly when they are used as a trap crop. If nasturtium plants become heavily infested with pests like aphids, it is wise to remove and dispose of the affected plants or treat them directly to prevent the pest population from growing too large and spreading to other garden areas.
Different nasturtium varieties have distinct growth habits that influence their best use in companion planting. Vining or trailing types are suitable for ground cover, climbing trellises, or cascading from containers, offering broad coverage and weed suppression. Bushier or compact varieties are better suited for interplanting within vegetable beds or as edging plants, where space is more limited.
Nasturtiums thrive in full sun and prefer well-drained, even poor, soil. Rich soil can lead to more foliage and fewer flowers, reducing their attractiveness to pollinators and beneficial insects. Ensuring these basic needs are met helps the nasturtiums grow vigorously and perform their companion planting duties effectively.