English ivy is a popular groundcover but it has spread beyond the garden and has overtaken forests, displacing native plant species across the United States. It forms both mats which cross the forest floor and woody vines which climb trees (up to 100'). These mats and vines block out sunlight, preventing native plant germination and killing trees. The plant spreads through runners and wildlife disperses its seeds.
In the shade, English ivy leaves are lobed (2 to 3 leaves per leaf), dark green with white veins, and waxy. In the sun, or on mature vines, the leaves can also be oval. Leaves are arranged alternately along the stem. Both groundcover and vines will produce clusters of small, dark purple fruits. During the summer, mature vines exposed to sun will also produce yellow flowers.
Fact Sheet: English Ivy
Photo credit: Forest & Kim Starr, Starr Environmental, Bugwood.org