Nasturtiums (Tropaeolum majus) feature vibrant flowers and a growth habit that can be vining or bushy. Both the peppery leaves and colorful flowers are edible. Companion planting involves placing different plant species near each other to create a mutually beneficial environment. Understanding which plants thrive alongside nasturtiums helps manage pests and maximize garden space.
Protecting Vulnerable Crops
Nasturtiums are particularly useful in the garden as a “trap crop” due to their strong attraction to certain garden pests. The plants emit compounds that specifically lure insects away from high-value vegetable crops. This function is most effective against aphids, which readily colonize nasturtium leaves instead of moving onto nearby plants.
Brassicas, such as cabbage, broccoli, and kale, frequently suffer from aphid infestations that stunt growth and ruin harvests. Planting nasturtiums along the borders or interspersed within the rows of these cole crops can significantly reduce pest pressure on the vegetables. The nasturtiums act as a sacrificial plant, diverting the attention of the small, soft-bodied insects.
The mechanism relies on nasturtiums being a preferred host, making them a more appealing target than the surrounding produce. This protective strategy is also beneficial for tomatoes and squash, which can be vulnerable to whiteflies and specific types of squash bugs. By drawing these insects away, the primary crops can focus their energy on healthy foliage and fruit development.
Regular monitoring of the nasturtiums is part of the trap cropping strategy, as they will quickly show signs of infestation. When the trap crop becomes heavily covered in aphids, the gardener should remove and dispose of the affected nasturtium leaves to prevent the population from becoming overwhelming and spilling over onto the protected plants. This proactive management maintains the integrity of the harvest without relying on pesticides.
The presence of nasturtiums has also been noted to repel certain beetles, including some varieties of cucumber beetles. This dual action of attracting some pests while deterring others makes them a versatile addition to rows of susceptible vegetables like cucumbers and zucchini. The deep green leaves and bright flowers provide a robust, attractive defense barrier for many common garden vegetables.
Enhancing Garden Aesthetics and Health
Beyond pest management, nasturtiums offer structural and visual benefits when paired with other plants. Their sprawling, vining habit works well as a living ground cover, which helps shade the soil around taller, sun-loving plants. This shading action maintains a cooler, more consistent soil temperature and reduces water evaporation, benefiting plants that struggle in intense heat.
Tall flowering plants, such as sunflowers or cosmos, serve as natural trellises for vining nasturtium varieties, allowing them to climb vertically. This pairing creates a layered look, utilizing space efficiently and adding multiple tiers of color to the garden design.
Certain herbs also form beneficial relationships with nasturtiums by improving the immediate soil environment. Low-growing herbs like chives and basil can help deter soil-based pests that might affect nasturtium roots. Basil’s compact structure complements the spreading habit of nasturtiums.
Dill is another excellent companion, as its feathery foliage offers a textural contrast, and its flowers attract beneficial insects like parasitic wasps and ladybugs. These insects are natural predators of the aphids that the nasturtiums attract, creating a miniature, self-regulating ecosystem.
The dense foliage of nasturtiums can also suppress weeds, reducing competition for water and nutrients near other crops. Using them at the base of corn stalks or tomatoes helps keep the ground clear and moist. This natural mulching effect is a low-effort way to improve the vigor of surrounding plants.
Plants That Do Not Pair Well
While nasturtiums are generally cooperative, some plants should be kept at a distance due to competitive interactions or shared vulnerabilities. Heavy feeders, such as deep-rooted, long-season vegetables, compete intensely with nasturtiums for available soil nutrients. Plants like fennel should be avoided entirely, as they inhibit the growth of almost all neighboring plants due to allelopathic effects.
Planting nasturtiums near potatoes is not recommended because both plants share a susceptibility to the same diseases and pests, including the early blight fungus. Having two susceptible plants close together increases the risk of rapid disease spread throughout the garden bed. The intense competition for potassium and phosphorus also weakens both plant types.
Mint is another problematic companion because its aggressively spreading root system quickly outcompetes nasturtiums for both space and moisture. Its vigorous growth can easily choke out the more delicate root structure of the nasturtium. Keeping mint contained in pots or separate beds is advisable.
Any plant that requires a significantly different soil pH or moisture level than nasturtiums will not thrive in close proximity. Nasturtiums prefer moderately fertile soil and consistent moisture, so placing them next to drought-tolerant, low-nutrient-requiring plants will result in one species suffering.