Common ivy
Common ivy (Hedera helix), also called English ivy or simply ivy, is an evergreen climbing plant in the family Araliaceae, native to most of Europe and western Asia.[1] It holds onto walls, fences and tree trunks with small aerial roots, and it will cover almost any surface that stays still long enough.
The plant has two stages of life. Young stems creep and climb, carrying lobed leaves. Once a stem reaches light at the top of its support it changes form, growing upright branches with plain oval leaves, clusters of small green flowers and dark berries that birds eat through the winter.[2]
Description[edit]
Climbing stems can reach 30 m (98 ft) when a tall tree or building gives them support. Without support the plant spreads across the ground as a dense mat, rooting wherever a stem touches soil. The bark of old stems becomes grey and fibrous, and trunks as thick as an arm are common on old walls.[1]
Leaves on the climbing stems have three to five lobes and are dark green with pale veins. Their shape varies a great deal between plants, which is one reason nurseries sell hundreds of named cultivars with speckled, golden or finely cut leaves.[3]
Flowers and fruit[edit]
The flowers appear in round umbels late in the year, when few other plants are in bloom. They are small and yellowish green, rich in nectar, and busy with bees, hoverflies and wasps on sunny days. The berries ripen through winter and turn almost black by spring.[2]
Growth habit[edit]
Ivy does not feed on the surfaces it climbs. The aerial roots only grip, pressing into cracks and pores and releasing a sticky substance that dries into a strong bond. On sound brick this does little harm, but on crumbling mortar the roots widen existing gaps and let water in.[4]
Stems grow toward shade while young and toward light once mature, so a young plant will search along the base of a wall for a dark crevice before it starts to climb. A healthy plant can add a couple of metres in a good year.
| Surface | Grip | Typical cover after five years |
|---|---|---|
| Old brick | Strong | Most of a two storey wall |
| Rendered wall | Moderate | Patchy, lifts in places |
| Tree bark | Strong | Trunk and lower branches |
| Painted metal | Weak | Needs wires to climb |
Ecology[edit]
Few plants give wildlife as much through the cold months. Birds nest in the thick cover, insects shelter behind the leaves and the late flowers feed pollinators that would otherwise go hungry in autumn. The berries are an important food for thrushes and pigeons when other fruit has gone.[2]
Outside its native range the plant can become an invasive species. In some coastal forests it smothers the ground layer and climbs into the canopy, where the extra weight and shade can weaken host trees over many years.[5]
Cultivation[edit]
Ivy tolerates deep shade, poor soil and neglect, which makes it popular for difficult corners, ground cover under trees and trailing baskets. Cuttings root easily in water or damp compost. Most garden forms stay in their juvenile stage for years if they are trimmed back before they reach the top of their support.[3]
- Plant against a wall in autumn or spring and water until established.
- Trim in early spring, before birds start nesting.
- Keep stems away from gutters, window frames and roof tiles.
In culture[edit]
Ivy has a long history in art and poetry as a sign of loyalty and of life that continues through winter. Wreaths of ivy were worn at ancient festivals, and the plant still appears in winter decorations alongside holly. Old university buildings covered in climbers gave a whole group of institutions its informal name.
It is also a favourite of painters of ruins, where a curtain of leaves over broken stone says more about time passing than any date could.
References[edit]
- General botanical description, written for this demonstration page.
- Seasonal notes on flowering and fruiting, written for this demonstration page.
- Notes on garden forms and propagation, written for this demonstration page.
- Notes on aerial roots and masonry, written for this demonstration page.
- Notes on spread outside the native range, written for this demonstration page.