Companion planting with gladiolus involves selecting plant partners that create a harmonious and mutually beneficial garden ecosystem. From a botanical perspective, the goal is to pair plants that have complementary growth habits, nutrient needs, and pest management profiles, thereby reducing competition and enhancing the overall health and beauty of the planting scheme.
Gladiolus are vertical accent plants with sword-like foliage and towering flower spikes. To create a visually balanced display, pair them with plants that offer contrasting forms. Low-growing, mounding, or sprawling plants help to conceal the often bare lower stems of gladioli while providing a "living mulch" that conserves soil moisture and suppresses weeds. Excellent choices include annuals like petunias and marigolds, or perennial ground covers like creeping thyme or catmint (Nepeta). The broad, dense foliage of hostas planted in front also creates a beautiful textural contrast with the gladiolus's upright form.
Gladiolus can be susceptible to pests like thrips and aphids. Strategically interplanting with species that naturally repel these insects is a core principle of companion planting. Garlic and alliums are superb companions as their strong scent is a known deterrent to many common pests, including those that target gladiolus corms and flowers. Similarly, the distinct aroma of marigolds (Tagetes species) repels nematodes in the soil and discourages aphids above ground. For a trap cropping strategy, planting nasturtiums nearby can lure aphids away from your prized gladiolus spikes, sacrificing themselves for the benefit of the primary crop.
Gladiolus are heavy feeders, requiring ample nutrients, particularly phosphorus, for strong bloom production. It is beneficial to avoid planting them next to other intensely greedy feeders that would directly compete for these resources. Instead, pair them with light to moderate feeders. Many herbs, such as lavender or oregano, fit this category and also provide the added benefit of pest repellency. Furthermore, consider plants with different primary growth periods. Planting quick-growing, shallow-rooted annuals like lettuce or spinach around gladiolus allows for a harvest before the gladiolus plants reach their peak size and nutrient demand.
From a plant-centric perspective, some species make poor companions for gladioli. Avoid planting them with aggressive, spreading plants that can easily outcompete gladiolus for water, light, and nutrients, such as some types of mint. It is also generally advised to avoid pairing them with very large, dense shrubs or trees that would cast excessive shade, as gladiolus require full sun to thrive and develop strong stems. The most significant incompatibility is with other members of the iris family (Iridaceae), to which gladiolus belong. Planting them closely together can facilitate the rapid spread of shared fungal diseases like fusarium rot and botrytis blight through the soil.
