Evergreen shrub from the Atlantic margin of Europe introduced to and spreading in many parts of the world. In the tropics it forms monotypic stands in mountainous areas subjected to large herbivore disturbance and/or fire.
Much-branched evergreen shrub to 2-4 m tall.
In SW Britain U. europaeus hybridizes with U. galli Planch. where their flowering periods may overlap. It exhibits much intra- and inter- population variation in morphology. Leaves are present only at the seedling stage but thereafter are replaced by spines or scales.
The hermaphrodite yellow flowers are usually insect-pollinated and 1 to 3 of them are bone on axillary clusters. Pods (2 cm long) open explosively releasing 2 to 6 seeds and the seeds (6.2 mg, 3.3 x 2.3 mm) may be further dispersed by ants. Seeds can germinate after been subjected to temperature up to 88°C. A persistent seed bank is formed as some seeds remain viable for up to 28 years in the soil. In Britain flowering time varies from January to May according to latitude and set seeds two months later. Seed germination and seedling survival is lower under a U. europaeus canopy than in the open.
When cut it coppices freely and following fire seed germination leads to high densities of seedlings. Shoot layering occurs. The species forms nitrogen-fixing root nodules. Its rooting system is shallow with a deep tap root.
Seedlings are often found at sites with some bare ground. Its nitrogen fixing capacity allow growth under conditions of extreme infertility. The shrub is light demanding and dies through shading but seedlings may become established under its own canopy. Bushes start degenerating after 20 years unless fire occurs.
It has potential for land reclamation and has been used as a hedge plant and for binding soil on dry sandy banks. On marginal land it is a source of food for cattle and ponies and formerly, after removal of spines, it was used for fodder.
Extensively distributed in the Atlantic part of Europe. Scattered throughout central Europe where it is thought to be naturalised. Rarely found in forests apart from forest edges. May form monotypic stands in disturbed areas.
Temperate oceanic climate with mild winters and mild to cool summers.
Requires disturbance, such as fire or large grazing herbivores, for establishment. Absent from arable and wetland habitats.
Very common in disturbed habits such as wasteland, river banks, quarry spoils, roadsides and railway embankments. Has increased since the 1950s after myxomatosis dramatically reduced rabbit populations.
A large number of insects have found feeding on the shrub, but at very low densities.
Introduced to many montane regions of the tropics, including Peru, La Réunion, Sri Lanka, St Helena and Hawai'i. U. europaeus is now naturalized in Sri Lanka and is considered a serious pest on two Hawaiian Islands. It was inadvertently introduced prior to 1910 when the wool industry was established. The species was introduced to many temperate regions and is a serious pests. In La Réunion it has extensively invaded heathlands, particularly in areas disturbed by cultivation and grazing. It forms monotypic stands in South America including in areas previously forested. Invasive in many temperate areas were the plant was often used as hedge material.
U. europaeus forms impenetrable and often extensive thickets with as many as 60,000 stems/ha. Its poor long-distance dispersal ability ensures that few distant founder populations are started. During the 1930s Hawaiian ranchers converted to cattle ranching and U. europaeus, until then controlled by sheep grazing, began to increase. Microsites produced by the hooves of large herbivores are ideal for gorse seedling establishment, gorse being a poor competitor. Drought and associated removal of grazing pressure appear to have contributed to the infestations.
It grows as low as 460 m a.s.l. but most of its distribution is between 630 and 2220 m. In South America the shrub is found up to 3200 m.
Range land vegetation often on site of former forests.
Not reported but presumably are few and have no significant effect.
In La Réunion it is said that U. europaeus has a higher combustible biomass and is probably more flammable than the native vegetation. In some parts New Zealand it has been suggested that stands of U. europaeus facilitate the regeneration of native forest trees. Its presence results in some soil acidification.
U. europaeus represents a fire hazard to private property. It invades watersheds which supply a substantial amount of drinking water. It is threatening agricultural and grazing lands. Thickets are impenetrable to humans and have persistent spiny litter.
In Hawaii, temporary control was undertaken in the 1970s using 2,4-5 T. The ban of the herbicide and lack of funding ended the programme. A task force was later set up to coordinate a management approach which included the following four control programmes: a/ containment: using Tordon 22K strips along roadsides were first targeted to eliminate the possibility of seed transport to new areas, b/ long-term biological: search for control agents in Europe which in 1984 resulted in the release of a seed weevil (Apion ulicis Forster). The weevil is now well established and spreading, but despite destroying 50% of seeds it had no detectable impact on the spreading populations c/ reforestation: using mainly native trees to shade out U. europaeus and d/ grazing: use of goats (Capra hircus) after fire.
No clear evidence is available but it appears that no equivalent species occur in any of the tropical regions invaded.
Unusual case of a species with a temperate Atlantic distribution invading mountainous tropical regions as well as other temperate regions. However in all reported cases both in native and invaded ranges U. europaeus regeneration is highly favoured by the production of microsites by large hoofed mammals, particularly cattle. Differences in seedbank have been found between temperate regions.