Vinca plants are valued for their continuous color, but they often develop a sparse or “leggy” growth habit instead of a dense, full shape. The term Vinca refers to two distinct groups: the popular annual Catharanthus roseus (Madagascar Periwinkle), and the perennial groundcovers Vinca minor and Vinca major. Although their botanical classifications differ, the principles for transforming their naturally sprawling tendencies into a compact, well-branched form are largely the same. Achieving a bushy Vinca involves manipulating the plant’s natural growth hormones, optimizing its environment, and managing its nutrient and water intake.
The Essential Technique of Pinching and Pruning
The primary reason a Vinca plant grows tall and thin is apical dominance. This phenomenon is driven by the plant hormone auxin, which is produced in the apical meristem, or the tip of the main stem. Auxin travels downward, inhibiting the growth of lateral buds along the stem, ensuring the main shoot continues to grow upward faster than side branches.
To counteract this dominance and force the plant to grow outward, gardeners use “pinching.” Pinching involves removing the soft, newly formed growing tip of a stem, typically using the thumb and forefinger. This action immediately removes the source of auxin production, causing the hormone’s concentration to drop significantly. This reduction allows the dormant lateral buds lower down on the stem to “break” and develop into new side shoots.
For initial shaping, pinching soft growth is sufficient. However, for older, woodier stems, pruning shears are necessary to cut back to a set of healthy leaves or a node. Timing is important; the best results come from pinching early in the season when the plant is actively growing. Repeating the process throughout the summer maintains the desired density, as removing terminal growth redirects energy into side shoots, resulting in a bushier appearance.
Optimizing Light Exposure for Density
Insufficient light intensity is a common cause of leggy growth that pruning alone cannot fix. When Vinca is placed in inadequate sunlight, it exhibits etiolation, a survival mechanism. Etiolation is the plant’s attempt to stretch quickly toward a light source, resulting in long, spindly stems with pale, widely spaced leaves.
This stretching is characterized by elongated internodes, the spaces along the stem between leaf nodes. High light intensity suppresses cellular elongation, promoting compact growth with robust stems and thicker leaves. Vinca performs best and maintains the most compact habit in full sun, requiring at least six to eight hours of direct sunlight daily.
If a plant begins to stretch, the elongated internodes will remain. However, relocating the plant to a brighter spot ensures all subsequent growth is dense and full. For plants in the ground, trimming surrounding shrubs or trees that cast excessive shade increases light duration and intensity. This environmental adjustment works alongside pruning to prevent new side shoots from becoming weak and stretched.
Fertilizing and Watering for Compact Growth
Nutrition and moisture levels are factors that encourage compact growth or contribute to a leggy appearance. When fertilizing Vinca, avoid formulas excessively high in nitrogen (N), the first number in the NPK ratio. High nitrogen promotes rapid vegetative growth, resulting in soft, succulent stems and large leaves at the expense of a firm, bushy structure.
A balanced, all-purpose fertilizer, such as a 10-10-10 blend, is recommended. Alternatively, use a formula with a slightly higher percentage of phosphorus (P) and potassium (K) to encourage strong root development and flowering. Controlling the nitrogen input manages the plant’s growth rate, preventing the rapid, soft elongation that leads to leggy stems. Some Vinca varieties are light feeders and may not require fertilizer if planted in rich soil.
Watering practices also influence growth, as Vinca is naturally drought tolerant once established. Overwatering is a common mistake that leads to weak, stretched stems and root issues. Allowing the soil to dry out slightly between waterings is preferable. Moderate water stress encourages the plant to develop a stronger, more resilient, and compact growth structure. Water should only be applied when the top one to two inches of soil feel dry to the touch.