Approximately 100 shrubs and small trees belong to the Rhamnus plant genus. The plant family members, commonly called "buckthorns", grow throughout the Northern Hemisphere and subtropical Southern Hemisphere. Both deciduous and evergreen, they reach a height of up to 25 feet depending on the variety. The trees within the Rhamnus genus can reach a trunk diameter of up to 10 inches. The plant family is highly invasive in North America, where it was widely imported and cultivated due to its deer resistance.
It is believed that the glossy and common buckthorn were introduced to North American from Europe and northern Africa prior to the 19th century. The shrubs and trees were transported aboard commercial sailing vessels, according to the Invasive Plant Watch Network. The plants quickly became widespread as ornamental hedges. In 1849 the shrub was widely planted as hedgerows in Wisconsin.
Despite its invasive potential buckthorns (Rhamnus) are still widely planted in home landscapes where deer populations are high because they rarely suffer damage from the foraging animals. Deer have a strong distaste for buckthorns (Rhamnus) and rarely consume them unless it is a necessity. The shrub or tree can be damaged during the winter months when the food supply is low and the deer will eat virtually anything to survive.
Effects on Native Plant Life
Buckthorns (Rhamnus) grow in either dry or wet planting locations with ease. The shrubs and trees pose a special danger to riparian areas where they quickly establish themselves and choke out native plant life. The plants are widely avoided by most insect pests and suffer from few diseases. The plant's vigorous growth and prolific foliage quickly shades out native plants.
Deer avoid the berries of the Rhamnus because they are toxic and unpalatable. A few birds, such as the European Starling are capable of consuming the berries despite the poisons they contain. Once the berries are consumed they have a laxative effect on the birds which helps to spread the seeds to wide ranging locations.
The Rhamnus plant genus offers gardeners numerous deer-resistant shrub and tree choices to consider when planting a deer-proof landscape. The deer will normally nibble on the plant but once they find out that it tastes bad they quickly cease consuming it. Care should always be taken when planting the Rhamnus to make sure that it does not escape cultivation. Certain varieties, such as the glossy and common buckthorn, should be avoided in locations where they have become invasive and a danger to native plant life.