Nasturtiums (Tropaeolum majus) are vibrant, easy-to-grow annuals prized for their edible, peppery flowers and distinctive, shield-shaped foliage. They are popular additions to gardens, working well as ground cover, in containers, or climbing up supports. Achieving the best display depends heavily on providing the correct physical space. Proper planting distance maximizes both the plant’s health and its overall appearance.
Why Nasturtium Spacing Matters for Health and Bloom
Incorrect spacing compromises the health and flowering of nasturtiums. Overcrowding restricts airflow around the leaves and stems, allowing moisture to linger. This humid environment creates ideal conditions for fungal diseases, such as powdery mildew.
Closely packed plants also compete intensely for sunlight, water, and nutrients in the soil. This competition reduces the energy available for flower production, resulting in fewer blooms and a sparser overall appearance.
Nasturtiums are often used as a trap crop for aphids, but excessive density can turn a minor issue into a severe infestation. When plants are too close, pests easily migrate, overwhelming the entire patch quickly. Adequate space ensures each plant can fully photosynthesize and remain dry, boosting its resistance to disease and pests.
Standard Planting Distance Guidelines
For general garden planting, the recommended final spacing for nasturtiums is 10 to 12 inches apart. This distance allows a mature plant enough room to spread its foliage without touching neighbors while still creating a full look. This spacing is suitable for borders and mixed beds.
When planting seeds directly, sow them about 4 inches apart. Once seedlings emerge and develop true leaves, they must be thinned out to the final spacing of 10 to 12 inches to prevent overcrowding. The final distance should be at least 12 inches to ensure sufficient room for growth and air circulation.
Transplanting nursery starts requires careful handling because nasturtiums are sensitive to root disturbance. It is important to handle transplants carefully and place them at the final desired distance right away. A common spacing for transplants is 10 to 14 inches apart, which accounts for the immediate presence of a larger root ball.
Adjusting Spacing for Different Varieties
Nasturtiums are categorized into two primary growth habits, and spacing should be tailored to the variety chosen. Trailing or vining types (Tropaeolum majus) are vigorous growers that can produce stems up to 10 feet long. If these varieties are intended to climb a trellis or cascade over an edge, they require wide spacing to accommodate their extensive reach.
A generous spacing of 12 to 18 inches apart is appropriate for vining types to ensure they have structural space to spread without tangling. Dwarf or bush varieties (Tropaeolum minus) are much more compact, typically reaching 10 to 12 inches in height and width. These compact plants can generally be spaced 6 to 10 inches apart to achieve a dense, mounding effect suitable for borders or small containers.
The minimum 6-inch spacing still provides the necessary air circulation to prevent fungal issues like powdery mildew. While a slightly denser planting is acceptable in hanging baskets or containers for immediate visual impact, these plants will require more frequent watering and potentially aggressive pruning to maintain health.
Sowing Depth and Thinning for Final Placement
Achieving the correct final spacing begins with the initial sowing depth, which influences successful germination. Nasturtium seeds are relatively large and should be planted between 1/2 to 1 inch deep in the soil. This depth ensures the seed has adequate contact with moisture and is protected from light, which is necessary for germination.
When direct sowing, plant two or three seeds in a small group to ensure at least one sprouts. Once seedlings emerge and grow a few sets of true leaves, they must be “thinned” to the strongest single plant in each group. The process involves gently pinching or clipping the weaker seedlings at the soil line, leaving the most robust one to grow into the final plant.
Thinning is how the gardener ensures the surviving plant is positioned at the correct final spacing. This step eliminates competition for resources at the earliest stage, setting up the remaining seedling for healthy, unhindered growth.