On level ground ivies remain creeping, not exceeding 5–20 cm height, but on surfaces suitable for climbing, including trees, natural rock outcrops or man-made structures such as quarry rock faces or built masonry and wooden structures, they can climb to at least 30 m above the ground.

Ivies have two leaf types, with palmately lobed juvenile leaves on creeping and climbing stems and unlobed cordate adult leaves on fertile flowering stems exposed to full sun, usually high in the crowns of trees or the tops of rock faces, from 2 m or more above ground.

The flowers are greenish-yellow with five small petals; they are produced in umbels in autumn to early winter and are very rich in nectar.

The fruit is a greenish-black, dark purple or (rarely) yellow berry 5–10 mm diameter with one to five seeds, ripening in late winter to mid-spring.

In Europe, the harm is generally minor although there can be competition for soil nutrients, light, and water, and senescent trees supporting heavy ivy growth can be liable to windthrow damage.

"[6] Harm and problems are more significant in North America, where ivy is without the natural pests and diseases that control its vigour in its native continents; the photosynthesis or structural strength of a tree can be overwhelmed by aggressive ivy growth leading to death directly or by opportunistic disease and insect attacks.

Ivies create a dense, vigorously smothering, shade-tolerant evergreen groundcover that can spread through assertive underground rhizomes and above-ground runners quickly over large natural plant community areas and outcompete the native vegetation.

[15] Drought-tolerant H. canariensis and H. algeriensis and European H. helix were originally cultivated in garden, park, and highway landscaping, but they have become aggressively invasive in coastal forests and riparian ecosystems, now necessitating costly eradication programs.

The name ivy derives from Old English ifig, cognate with German Efeu, of unknown original meaning.

[11] Old regional common names in Britain, no longer used, include "Bindwood" and "Lovestone", for the way it clings and grows over stones and bricks.

Like many other evergreen plants, which impressed European cultures by persisting through the winter, ivy has traditionally been imbued with a spiritual significance.

The image of ivy-covered historic buildings gave the name Ivy League to a group of old and prestigious American universities.