January

Ivies

by Clare Coleman

The WFS diary lists the familiar common ivy, Hedera helix but ivies are more interesting than you would think! There are in fact two subspecies of the H. helix and at least two other alien ivies which have become naturalised in Britain.

Identifying alien (i.e. non-native to the British Isles) plants can be tricky as few are illustrated in the usual field guides. However, the Plant Crib on p 216 - 218 has excellent tips on Hedera with some drawings of leaf shapes. Stem hairs are also important distinguishing features of ivies, so a hand lens is recommended.

H. colchica (Persian Ivy) is an established garden escape and can be locally abundant. It originates from Eastern Europe and Turkey. There is a well known site on Weybridge Common, Surrey. It has large (10cm +), leathery dark green cordate (heart shaped) leaves. The stem hairs are golden brown whereas those on H. helix are white.

H. helix subsp. canariensis or H. algeriensis (Algerian Ivy) is less common than H. colchica. It also has large leaves but the leaf bases are rounded rather than cordate (see p 989, figures C & D in Stace for an illustration of these different leaf bases) and is more glossy than H. colchica. Both the above Hedera have semi-peltate (basin-shaped) stem hairs whereas the next two species both have stellate (star-shaped) hairs.

H. helix subsp. helix (Common Ivy) and H. helix subsp. hibernica (Atlantic Ivy) are tricky to distinguish. Always use young stems when looking at the hairs to distinguish these species and look for the following characteristics:

Character H. helix subsp. helix H. helix subsp. hibernica
Leaves < 8 cm > 8 cm
Hairs on leaves Grey white rays of hairs projecting in all directions Yellow and lying parallel to the leaf surface
Stem densely hairy Downy
Habitat Needs base-rich soils and does not tolerate acid soil Tolerates wide range of soils; more common in the west of the UK; can colonise unstable rock and storm beaches
Sap strong sweet odour weak, bitter odour

Forunately there is no reported hybridization amongst ivies.

 

Further reading and references

The BSBI handbook on aliens plants by E Clement and C Foster contains useful references on where to find species illustrations.

Rose, PQ (1980) Ivies

Stace, CA (1975) Hybridization and the Flora of the British Isles

Stace, CA (1997) New Flora of the British Isles

Rich, T & Jermy, AC (1998) Plant Crib