English ivy (Hedera helix) is a member of the Araliaceae or Aralia family, related to common plants like Schefflera and Fatsia. It is native to western Asia, North Africa and Europe, but has naturalized widely in the United States. The most distinctive features of English ivy are the climbing stems and the evergreen leaves. The Latin species name, "helix," comes from a Greek word that means "to roll or wrap," probably referring to the vine's tendency to wrap itself around any support. Hedera helix is distinguished by its unusual growth habit.
Young English ivy leaves are dark green and 2 to 3 inches long. Each has five distinct lobes. When leaves reach the adult stage, they lose their lobed appearance and become oval-shaped or eliptical. The stems climb by clinging to supporting structures with small roots. The plants produce flowers in the fall after young branches reach about 15 feet tall or reach the top of a particular support. The flowers are followed by black fruits. Without support, the ivy can spread 2 to 10 feet along the ground. With support, English ivy can reach 50 to 90 feet tall.
Growth: Seeking Nutrition
Long branches of spreading English ivy often root in the soil, and the roots mature to provide nutrition to the plants. Climbing ivy anchors itself with root-like structures, but when the branches adhere to trellises or buildings they cannot provide the plant with nutrition. If ivy climbs and adheres to trees, it can injure them by pulling nutrients from the host tree.
Growth and Habitat Qualities
When climbing ivy flowers, it provides nectar to bees. This is particularly important, as the plants flower in autumn, when other flowers have died back. The pea-size fruits of climbing English ivy also provide food to a variety of birds. Creeping ivy never flowers or fruits and has less value as a habitat plant.
According to Liberty Hyde Bailey in "Hortus Third," the juvenile shoots of English ivy mutate freely and this growth characteristic has produced many varieties featuring variations in growth habit and leaf forms and colors. Breeders have taken advantage of this trait to create new varieties.The University of Minnesota's Plant Information Online database includes 334 listings for Hedera helix cultivars. Among them are variegated types, with bi-colored foliage; dwarf, non-climbing types and varieties with uniquely shaped leaves, like the eponymous 'Webfoot' variety.
Because of its extreme vigor, the species form of English ivy is considered a noxious weed in some places, including the American South and Pacific Northwest. Unlike some other species, where seeds are dispersed by birds or other animals, English ivy is primarily dispersed by humans who use it for plantings. In disturbed spaces and open woodlands, the ivy expands outward to form a dense mat, crowding out native species and creating a monoculture. Mechanical control (slow and labor intensive) is the primary means of eradicating English ivy.