In the 1980s, beach vitex was introduced to South Carolina's coast for erosion control and has since spread on to North Carolina's dunes. The plant produces tens of thousands of seeds and can also reproduce from shoots.
Beach vitex grows as a short (1 - 2' in height) shrub and puts out runners which sprawl from the shrub for as far as 60'. Woody stems can easily break off, disperse through water, and reproduce in other locations along the coast. Leaves (1 - 2") are oval, pale green with a silvery underside. Showy purple flowers bloom in small clusters all year-round. It also produces small mauve fruits (1/4" diameter).
Fact Sheet: Beach Vitex
Melanie Doyle and Dale W. Suiter - Status of Beach Vitex in North Carolina
Photo credit clockwise: Forest & Kim Starr, Starr Environmental, Bugwood.org