Nasturtiums are popular annuals known for their vibrant, edible flowers and distinctive, lily-pad-like leaves. Gardeners often appreciate them for their beauty and ease of growth. Despite their reputation for being low-maintenance and prolific bloomers, it can be frustrating when nasturtium plants produce lush foliage but few or no flowers. This article clarifies why nasturtiums might not be blooming and outlines practical steps to encourage abundant flowering.
Ideal Conditions for Nasturtium Blooms
Nasturtiums generally thrive and produce numerous blooms when their specific growing preferences are met. They perform best in locations receiving ample sunlight, ideally six to eight hours of direct sun daily, for prolific flowering. While nasturtiums can tolerate partial shade (three to six hours of sunlight), blooms may be less abundant.
These plants prefer lean, well-draining soil rather than rich, highly fertile ground. Soil too rich in nutrients, especially nitrogen, often leads to excessive leafy growth at the expense of flower development. Well-draining soil also prevents waterlogging, which can harm the plant.
Nasturtiums prefer consistent moisture but are somewhat drought-tolerant once established, needing about one inch of water per week. Container-grown plants may require more frequent watering. Mild temperatures are favored; nasturtiums are sensitive to frost and can stress in extreme heat, reducing flowering.
Why Your Nasturtiums Aren’t Flowering
Excessive Nitrogen
An overabundance of nitrogen in the soil is a common reason nasturtiums fail to flower. Nitrogen promotes vigorous leafy growth. When nasturtiums are planted in rich soil or receive high-nitrogen fertilizers, they channel energy into producing lush foliage instead of flowers, resulting in abundant green leaves but few blooms.
Insufficient Sunlight
Nasturtiums require adequate sunlight for flower formation. If plants receive too little direct sunlight, they may produce spindly growth and significantly fewer flowers. In deeply shaded conditions, nasturtiums might struggle to produce any blooms, or flowers could be short-lived and underdeveloped.
Overwatering or Poor Drainage
Waterlogged soil severely stresses nasturtium plants, inhibiting flowering. When roots sit in soggy soil, they are deprived of oxygen, leading to root rot and plant decline. This stress diverts the plant’s energy towards survival instead of flower production. Poor drainage exacerbates this by trapping excess moisture.
Pest Infestations
Pest infestations weaken nasturtium plants, diverting energy from flowering. Aphids are a common pest, clustering on new growth and leaf undersides. These sap-sucking insects deplete the plant’s vital fluids, leading to stunted growth, distorted leaves, and reduced flower production. Nasturtiums are often used as a “trap crop” due to their susceptibility.
Environmental Stress
Environmental stressors can impede nasturtium flowering. Extreme temperatures, especially prolonged heat, cause plants to stress and cease blooming. Cold snaps and frost can also damage plants and prevent flower development. Overcrowding leads to competition for light, water, and nutrients, stressing plants and reducing flowering potential.
Strategies to Promote Flowering
Adjusting fertilization encourages nasturtium blooms. If your soil is rich, avoid additional fertilizers, as nasturtiums thrive in less fertile conditions. For plants in poorer soil, use a low-nitrogen, balanced fertilizer or one with higher phosphorus to promote flowering over leaf growth. Apply fertilizer sparingly, perhaps once a month during the growing season, if needed.
Optimizing light exposure is crucial for abundant nasturtium flowers. Ensure plants receive at least six hours of direct sunlight daily. If plants are in shade, relocate them to a sunnier spot or prune blocking foliage. In hot climates, afternoon shade can prevent stress while still ensuring enough morning and early afternoon sun for blooming.
Improving watering practices supports healthy nasturtium growth and flowering. Water deeply, allowing the soil to dry slightly between waterings to prevent root rot. For container plants, check soil moisture regularly, as pots dry out quickly. Ensure good drainage through appropriate soil composition or containers with drainage holes to prevent waterlogged conditions.
Effective pest management helps restore a nasturtium’s energy for flowering. Regularly inspect plants for common pests like aphids, especially on new growth and leaf undersides. For light infestations, a strong water spray can dislodge pests. Introducing beneficial insects like ladybugs or lacewings can also naturally control aphid populations.
Managing environmental factors, such as proper spacing, reduces plant stress and encourages better flowering. Allow adequate space between nasturtium plants for good air circulation and to reduce competition for resources. Protecting plants from temperature extremes, like providing temporary shade during heatwaves or covering during cold snaps, helps maintain their health and blooming capacity.