English ivy

Ivy growing on a granite crag, Czech Republic.   Stems showing the rootlets used to cling to walls and tree trunks. Hedera helix is an evergreen climbing plant, growing to 20–30 m (66–98 ft) high where suitable surfaces (trees, cliffs, walls) are available, and also growing as groundcover where no vertical surfaces occur. It climbs by means of aerial rootlets with matted pads which cling strongly to the substrate. The ability to climb on surfaces varies with the plants variety and other factors: Hedera helix prefers non-reflective, darker and rough surfaces with near-neutral pH. It generally thrives in a wide range of soil pH with 6.5 being ideal, prefers moist, shady locations and avoids exposure to direct sunlight, the latter promoting drying out in winter.The leaves are alternate, 50–100 mm (2–4 in) long, with a 15–20 mm (0.6–0.8 in) petiole; they are of two types, with palmately five-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 top of rock faces. The flowers are produced from late summer until late autumn, individually small, in 3-to-5 cm-diameter (1.2-to-2.0 in) umbels, greenish-yellow, and very rich in nectar, an important late autumn food source for bees and other insects. The fruit are purple-black to orange-yellow berries 6–8 mm (0.2–0.3 in) in diameter, ripening in late winter, and are an important food for many birds, though somewhat poisonous to humans. One to five seeds are in each berry, which are dispersed after being eaten by birds. SubspeciesEdit The three subspecies are: H. h. helix - central, northern and western Europe, plants without rhizomes, purple-black ripe fruit, H. h. poetarum Nyman (syn. Hedera chrysocarpa Walsh) - southeast Europe and southwest Asia (Italy, Balkans, Turkey), plants without rhizomes, orange-yellow ripe fruit, H. h. rhizomatifera McAllister - southeast Spain, plants rhizomatous, purple-black ripe fruit.The closely related species Hedera canariensis and Hedera hibernica are also often treated as subspecies of H. helix, though they differ in chromosome number so do not hybridise readily. H. helix can be best distinguished by the shape and colour of its leaf trichomes, usually smaller and slightly more deeply lobed leaves and somewhat less vigorous growth, though identification is often not easy.