Crocosmia, also known as Montbretia or coppertips, offers a vibrant display with its sword-like foliage and fiery, trumpet-shaped blooms. These striking plants add visual interest, particularly in late summer. A common concern for gardeners is Crocosmia stems falling over, especially as they mature or after flowering. Understanding the underlying causes is crucial for maintaining their upright habit.
Why Crocosmia Stems Fall Over
Several factors contribute to Crocosmia stems flopping. Strong winds and heavy rain can physically damage or weaken stems, causing them to bend or break. Insufficient sunlight leads to weak stems lacking rigidity to support height and blooms. Crocosmia requires at least six hours of direct sunlight daily for robust growth.
Growing conditions also impact stem strength. Overcrowding, with too many corms competing for resources, results in thin, spindly stems prone to flopping. Poor soil drainage or consistent overwatering weakens the root system, making the plant unstable and susceptible to bulb rot. An imbalance in nutrients, especially excess nitrogen, promotes lush foliage at the expense of strong stem development and flower production.
Crocosmia varieties also influence susceptibility to falling. Taller cultivars, like ‘Lucifer’, are more prone to flopping due to height, even in favorable conditions. Some types develop a growth habit where new corms form on top of older ones, causing the plant to “climb out of the soil” over time, reducing vigor and stability.
Preventing Crocosmia From Falling
Structural support immediately prevents Crocosmia stems from falling. Individual plants can be staked with bamboo canes or garden stakes, gently tying stems to the support as they grow. Grow-through supports or cages allow foliage to grow through the structure, offering comprehensive support for the clump. Planting Crocosmia in dense groups also offers mutual support, as plants lean on each other for stability.
Optimizing the growing environment is another effective preventative. Ensure plants receive ample sunlight for sturdy stem development. Improving soil drainage is crucial; incorporating organic matter like compost or grit into heavy clay soils prevents waterlogging and promotes a healthier root system. Consistent, deep watering is beneficial (about an inch weekly), but avoid constantly soggy conditions.
Managing plant density is essential for long-term health and upright growth. Crocosmia corms multiply, leading to congested clumps. Dividing overcrowded clumps every three to five years (ideally in early spring) reduces competition and allows stronger stem development. When planting new corms, space them adequately (4-6 inches apart, 3-5 inches deep) for proper air circulation and growth. Selecting shorter, more compact varieties also reduces flopping, especially in windy areas.
Long-Term Care for Strong, Upright Growth
Balanced fertilization supports strong, upright growth. Avoid high-nitrogen fertilizers, which encourage excessive leafy growth at the expense of stem strength and flower production. Instead, apply a balanced slow-release fertilizer for bulbs in early spring or incorporate well-rotted compost. This provides necessary nutrients for robust development without promoting leggy stems.
Deadheading spent flowers redirects the plant’s energy. Instead of expending resources on seed production, the plant channels this energy into strengthening its corms and overall structure, contributing to more vigorous growth in subsequent seasons. Allow foliage to remain after blooming until it naturally yellows and dies back, as these leaves are crucial for gathering sunlight and storing energy in the corms for the next year’s growth.
Promptly addressing pest and disease issues contributes to plant vigor. While generally resistant, Crocosmia can be affected by spider mites, especially in hot, dry conditions; a strong water spray often dislodges them. Fungal diseases like gladiolus rust (brownish spots) are less common but can occur in humid, low-light conditions; removing affected leaves and ensuring good air circulation helps. Healthy plants better maintain structural integrity.
Proper winter care supports long-term plant health. In zones where Crocosmia is hardy (USDA Zones 5-9), corms can remain in the ground. Applying a thick layer of organic mulch around the root zone insulates corms from severe cold snaps. In colder climates (Zone 4 and below), lifting corms after the first frost and storing them in a cool, dry place until spring planting ensures survival and promotes robust growth next season.