Vinca, commonly known as Periwinkle, is a popular choice for gardeners seeking a reliable, low-maintenance groundcover or a vibrant annual flower display. As deer habitats expand, many homeowners worry if their landscaping will become a food source. Horticultural experts agree that plants within the Vinca genus are highly deer-resistant, offering a strong defense against browsing. This resistance is consistent across all types of Vinca, which possess natural defenses that typically render them unpalatable to deer.
The Resistance Rating of Vinca Species
The term “Vinca” describes three distinct plants, all sharing a high level of resistance to deer browsing. The perennial groundcovers, Vinca minor and Vinca major, are hardy, evergreen vines seldom damaged by deer. Catharanthus roseus, often sold as Annual Vinca or Madagascar Periwinkle, also maintains a strong reputation for resistance. This flowering annual is a frequent choice for hot, sunny locations. University extension services, such as Rutgers University, often rate this plant as “Rarely Damaged” on their deer resistance scales, indicating they are among the least likely to be eaten.
The Chemical Reason for Deer Avoidance
The primary mechanism deterring deer from consuming Vinca is the presence of indole alkaloids. These plants belong to the dogbane family (Apocynaceae), which produces these compounds as a defense against herbivores. When a deer samples the plant, the alkaloids produce a distinctly bitter taste, immediately repulsive to the animal.
Beyond the bitter flavor, the alkaloids in Vinca species can be mildly toxic, causing digestive upset if consumed in significant quantity. Catharanthus roseus is the source of several potent alkaloids, including precursors to vinblastine and vincristine. These compounds function as a protective agent, signaling to the deer that the plant is not a safe food source, leading them to abandon it.
Environmental Factors That Increase Browsing Risk
Although Vinca is highly resistant, environmental pressures can increase the risk of browsing. A high local deer population that has exhausted its preferred food sources is a factor. When competition for food is intense, deer resort to “desperation browsing” on plants they would normally avoid.
Severe weather conditions, such as prolonged drought or heavy snow cover, also increase the likelihood of Vinca being eaten. During periods of extreme stress, deer are compelled to consume nearly any available vegetation, including plants with unpalatable alkaloids. Furthermore, newly planted Vinca may be more vulnerable, as younger plants may not have fully concentrated the defensive alkaloids that give mature foliage its bitter taste.