The term “ivy” is commonly used to describe any creeping or climbing vine, but the actual number of “types” depends on whether the classification is botanical or colloquial. Many plants share the name “ivy” due to their growth habit, which involves using aerial roots or tendrils to cling to surfaces like walls and trees. A clear distinction exists between the small group of plants considered true botanical ivy and the much larger collection of plants that merely share the common name.
The Botanical Classification of True Ivies
True ivies belong to the genus Hedera, which is part of the ginseng family, Araliaceae. The total number of accepted species within this genus is relatively small, generally ranging from 12 to 15 species worldwide. These species are evergreen woody vines native to parts of Europe, Asia, and northern Africa. They are characterized by their simple, lobed leaves and climb using specialized aerial roots that cling to surfaces.
The most widely recognized true ivy is Hedera helix, commonly known as English or Common Ivy, frequently used as an ornamental groundcover or wall climber. Other distinct species include Hedera hibernica (Atlantic or Irish Ivy) and Hedera canariensis (Canary Island or Algerian Ivy), known for their larger leaves. While numerous cultivated varieties and hybrids exist within the Hedera genus, they all trace their lineage back to this limited number of original species.
Plants Commonly Mistaken for Ivy
A much greater number of plants are referred to as “ivy” in everyday language, despite belonging to entirely different botanical families. The most well-known example is Poison Ivy, Toxicodendron radicans, which is not a true ivy but a member of the sumac family, Anacardiaceae. This plant contains an oily sap called urushiol, which causes an intensely itchy allergic rash upon contact. Poison Ivy is recognizable by its structure of three leaflets, growing as a vine or a shrub, and is widespread across North America.
Other common ornamental look-alikes include Boston Ivy (Parthenocissus tricuspidata) and Virginia Creeper (Parthenocissus quinquefolia), both belonging to the grape family, Vitaceae. Boston Ivy is often used to cover building facades and typically features simple, three-lobed leaves. Grape Ivy, a common houseplant, usually refers to Cissus rhombifolia, which is also in the grape family. These plants are often confused with true ivy due to their vining habit and similar leaf shapes.
Essential Identification Characteristics
Distinguishing true Hedera ivy from its common look-alikes involves observing a few distinct morphological features. True ivies, such as English Ivy, have simple leaves with three to five pointed lobes that alternate along a woody, often hairy stem. The leaves generally have a waxy, dark green, evergreen appearance year-round. The climbing method relies on small, dense aerial roots.
In contrast, the most important distinction for safety is recognizing Poison Ivy, which always has compound leaves made up of three separate leaflets, a pattern often summarized by the saying, “Leaves of three, let it be.” The center leaflet of Poison Ivy is on a noticeably longer stalk than the two side leaflets. While true ivy is evergreen, Poison Ivy is deciduous, meaning its leaves change color and drop in the fall. True ivies do not cause an allergic contact dermatitis rash.