Rhamnus alaternus
Photo by Flickr user Ettore Balocchi

Italian buckthorn

Ratings

  • This plant has a Plant Risk Evaluator rating of High Potential Risk
  • This plant has been rated Watch by the California Invasive Plant Council

Description

Italian buckthorn is an evergreen shrub that has been used for hedges. It is native to scrublands in the Mediterranean from Portugal across southern Spain, France, Italy to Albania, and Greece to as far north as the Crimean shores of the Black sea and south to Corsica, Sicily, and Sardinia.

The cultivar 'John Edwards' was introduced by the Saratoga Horticultural Foundation for its vigor, disease resistance, and longevity. The cultivar 'Variegata' has variegated leaves with cream-white horizontal stripes.

The concern with Rhamnus alaternus is that it is a widely used plant that seems to have overcome the reproductive invasion barrier of being dioecious (having male and female plants) to establish itself in multiple locations in the San Francisco Bay area over the past 3 to 4 years. If only male plants are used, they cannot reproduce with each other and spread by seed. But if they aren't completely dioecious, or there are female plants present, reproduction could happen. The variegated clone is a female plant, so there may be some crossing happening with those plants.

Why is this plant not included on the invasive plant list?

Italian buckthorn was included in the 2016 nursery survey and was found at only 1.7% of nurseries in the survey. It may be found more often at wholesale nurseries, but that is not captured in our survey of retail nurseries. A plant must be found in at least 3% of nurseries in the survey to be added to the plant list.