Companion planting with gladiolus involves selecting plant partners that create a mutually beneficial ecosystem. From a botanical perspective, the goal is to enhance growth, deter pests, improve soil health, and create a visually harmonious and structurally sound garden bed. The tall, vertical form and specific growth habits of gladiolus present unique opportunities for companion planting.
Gladiolus are particularly susceptible to thrips, tiny insects that feed on flower buds and leaves, causing streaking and deformation. From a defensive plant perspective, strong-smelling companions can help mask the presence of the gladiolus or actively repel these pests. Excellent choices include Alliums (such as garlic, chives, and ornamental alliums), which emit a sulfur compound that deters thrips, aphids, and even rodents. Similarly, basil and other aromatic herbs can confuse pests seeking their host plants. Alternatively, you can use the strategy of trap cropping by planting a more attractive host for thrips, like French marigolds (Tagetes patula), at a distance from your gladiolus patch to lure the pests away from your prized blooms.
The tall flower spikes of gladiolus, which can reach several feet in height, are vulnerable to wind and heavy rain. From a structural and competitive standpoint, planting lower-growing, bushy species around them can provide essential physical support and help anchor them in the soil. These companions also create a "living mulch," shading the soil to conserve moisture and suppress weeds that would otherwise compete with the gladiolus for water and nutrients. Ideal plants for this role are sturdy annuals and perennials such as peonies, dahlias, and zinnias. Their fuller form fills the space at the base of the gladioli, creating a lush underplanting that supports the stems and reduces the need for staking.
Gladiolus corms are typically planted in succession for a prolonged bloom time, but the foliage must be left to die back naturally to feed the corm for next year's growth. This can leave an unsightly period where yellowing leaves remain in the garden. From a lifecycle perspective, strategic companion planting can mask this fading foliage. Fast-growing annuals like cosmos, cleome, or tall salvia can be planted to fill in the gaps as the gladiolus finishes its bloom cycle. Aesthetically, the sword-like foliage and bold flower spikes of gladiolus contrast beautifully with plants that have different forms. The large, rounded flower heads of yarrow (Achillea) or the airy, delicate plumes of astilbe provide a stunning textural contrast, making the architectural form of the gladiolus stand out even more dramatically.
Not all plants make good neighbors. From a competitive and allelopathic perspective, it is best to avoid planting gladiolus with heavy feeders or plants that may inhibit their growth. Beans and peas, for instance, are aggressive growers that can outcompete gladiolus for soil nutrients and water. Furthermore, while not thoroughly proven, some gardeners advise against planting gladiolus near other bulbous plants like lilies or dahlias to avoid creating a concentrated target for shared pests and fungal diseases in the soil, practicing a form of crop rotation within the ornamental garden.
