The question of whether Vinca is drought tolerant has a nuanced answer because the common name “Vinca” refers to two distinct groups of plants with very different water needs. Its true drought tolerance depends entirely on which species you are considering. To understand this difference, it is necessary to identify the two plants that share this popular name and then examine their native environments. A clear understanding of these two species is the first step toward successful cultivation, especially in drier climates.
The Two Plants Called Vinca
The term “Vinca” is confusing because it is used for both an annual bedding plant and a perennial groundcover. The annual variety is Catharanthus roseus, widely known as Madagascar Periwinkle, and is grown as a seasonal plant in flower beds and containers. This species is an upright annual that produces masses of brightly colored flowers throughout the summer until the first frost.
The perennial group, commonly called Periwinkle or Creeping Vinca, belongs to the genus Vinca, which primarily includes Vinca minor and Vinca major. These perennial species are low-growing, evergreen groundcovers prized for their glossy foliage and spreading habit. They are used to quickly cover large areas, particularly in shady spots, and bear small blue or white flowers in the spring.
Drought Tolerance: A Tale of Two Species
The two plants called Vinca possess significantly different levels of drought tolerance due to their origins. The annual Vinca, Catharanthus roseus, exhibits a high degree of drought tolerance once its root system is fully established. Native to semi-arid regions of Africa, it prefers hot, dry conditions and flowers profusely under heat stress. Overwatering is a far more common cause of failure than drought, often leading to root rot and fungal diseases.
In contrast, the perennial species, Vinca minor and Vinca major, are only moderately tolerant of dry spells. While they can survive short periods without rain, they prefer sites with consistent moisture and partial to full shade. Extended drought conditions will cause stress, resulting in leaf burn, defoliation, and potential dieback, especially in sunny exposures. Both species perform best with about one to two inches of water per week, either from rain or irrigation.
Practical Water Management for Vinca
Successful cultivation of either Vinca species, particularly in drier environments, depends heavily on how water is managed during planting and establishment. The first few weeks after planting are a particularly vulnerable time for both the annual and perennial varieties, requiring consistent, deep watering to encourage the development of a robust root system. Allowing the plants to dry out too much during this initial phase, especially for newly transplanted annual Vinca seedlings, can cause severe stress that is difficult to reverse.
Soil composition plays a major role in regulating water for both plants, though for different reasons. Annual Vinca requires well-draining soil to prevent the waterlogged conditions that lead to its most common diseases, such as root rot. For the perennial groundcovers, incorporating organic matter helps the soil retain adequate moisture while still allowing for proper drainage.
Once established, the best technique for watering is to water deeply but infrequently. Applying water slowly at the base of the plant until the soil is moist to a depth of about six inches encourages roots to grow downward, increasing the plant’s resilience to dry conditions. Furthermore, a layer of organic mulch around the plants helps to regulate soil temperature and significantly reduces water evaporation from the soil surface.