Invasive Alien Species in Northern Ireland

Prunus laurocerasus, Cherry laurel

Prunus laurocerasus L.
 
Introduction
A large vigorous shrub or small tree found in demesnes and planted woodland; introduced for ornament by landowners or estate managers and widely planted in the nineteenth century.
 
Description
An evergreen shrub or tree, reaching about seven metres in height, and spreading out widely. It can form extensive dense shrubberies. It has large long, oval leathery and shiny leaves, with small teeth along their edges. Long, attractive, upright spikes of small pure white flowers are produced abundantly in April and are followed by small cherry–like fruits.
The plant is very poisonous to humans, with abundant cyanide content, and no parts should be eaten, although the flesh of the berries is reportedly harmless but tasteless.
Nectaries are produced both in the flowers and on the underside of the leaves, and it is a popular nectar source for various insects such as ants, ichneumons and hoverflies.
 
Country of origin
Its native range lies around the Black Sea, where it grows alongside native Rhododendron ponticum.
 
Current distribution
Now widespread across most of Ireland and Great Britain in estate woodland.
 
Location in Ireland
Virtually ubiquitous in all old estates, gardens and parks.
 
Life cycle
A conventional sexual species reproducing by seed. Some birds are reported to eat the berries and disperse the seed, but it is doubtful if this is a major factor in the spread of this species in Ireland. It will spread locally by layering and suckering.
 
Wildlife and habitat impacts
There are both positive and negative aspects to this plant’s impact on wildlife.
It can be an important nesting facility for birds and provides abundant nectar for many insects.
On the negative side, its rapid growth and the way it casts an all–year–round dense shade means that it shades out plants from the woodland floor, and generally out–competes less vigorous shrubs and young trees. Like Rhododendron ponticum with which it often grows, if unmanaged, it will form almost impenetrable shrubberies or understories in woodland and effectively kill off all other vegetation except the mature trees.
 
Human impacts
None except destruction of amenity landscapes by excessive unmanaged growth.
 
Key vectors
The wide distribution and spread of this species is entirely the result of deliberate planting, mainly in Victorian times.
 
What you can do as an individual
The problems caused by this plant are largely a result of lack of management of public and private parks and woodland areas; individual action is not recommended.
 
Advice to specific groups relevant to this species
None.
 
Management measures
The problems have arisen because of planting of this species followed by a lack of subsequent management.
Excessive growth of cherry laurel can be tackled by cutting back, and a subsequent continuing programme of pruning. However, the plant rapidly regenerates from cut shoots, and frequently produces suckers from the roots. Extermination may be desirable if the infestation is causing undesired effects on natural or semi–natural habitats, but this can be achieved only through physical, mechanical means, and is expensive and labour–intensive. To inhibit regrowth, herbicides are usually applied to cut stools. Application of herbicides to mature, uncut plants is ineffective.
 
Management groups
None known.
 
Further information
Links
None.
 
Literature
None.
 
Text written by:
Paul Hackney, Keeper of Botany, Ulster Museum