Gorse: Highly invasive invader in cooler climate conditions in the Upcountry

By Lalith Gunasekara

(March 05, Melbourne, Sri Lanka Guardian) Gorse (Ulex europaeus) plant is not very familiar to Sri Lanka even though it was introduced to the country in 1888. It has been invading natural ecosystems in the hill country especially in Horton Plains National Park. According to the survey conducted by some scientist from the University of Sri Jayawardenepura in 1997-1998 found that the extent and distribution of the gorse is the park is about 6 ha. If you are travelling through this wonderful place (World’s end) in Sri Lanka, you would be able to see this aggressive invader - gorse in cooler weather condition.

The gorse plant was originated in temperate climatic conditions in Europe and introduced to some countries as a hedge plant. It is sometimes called “furze” or “whin”. Gorse recorded as a serious weed in Hawaii, New Zealand, a principle weed in Australia and Chile and a common weed in Iran, Italy and Poland. Australia is spending million’s of dollars to manage gorse.

Gorse is a prickly, perennial, evergreen legume can grow up to 3 metres tall and 3 m across or more. All its stems are woody when mature and covered with spines up to 5 cm long. Leaves are dark green, hairy, narrow, spine-like and 1-3 cm long. They are evenly spaced along the stems in clusters. Flowers are bright yellow, pea shaped and about 2 cm long. They are produced in clusters mainly near the end of branches. The fruit is a dark pod, 1-2 cm long, covered in dense hair and containing 2-6 seeds. Seeds are green-brown, smooth and shiny, 3 mm long and triangular in shape with a paler aril. Gorse plants have no distinct taproot. The root system is dense but consists mostly of shallow fibrous feeding roots.

Gorse plants first flowering when they are about 18 months old. Flowers can be produced at almost all times of the year. In cool climates, gorse may flower only once a year. Seeds are released in hot or dry conditions and can be stimulated into germination following burning or mechanical disturbance. Gorse plant can live up to a maximum age of about 30 years. Ripe seeds burst from the pods when heated by the sun and may also be moved by ants. Birds may spread the seeds further and gorse plants are often found growing under trees where birds have perched. Earthworks and vehicles can also move seeds. Seed can remain dormant but viable for 75 years or longer, building up a huge seed bank in the soil.

Impacts:

Gorse is a major problem in native vegetation and forestry where plants compete strongly with young trees and thickets, increasing the fire hazard along the edges of plantations. It will also grow in pasture paddocks, resulting in lower carrying capacity and providing harbour for vermin. In the long term, soils under gorse become more acid and lose nutrients.

This plant is a big threat to the biodiversity of Horton Plains in Sri Lanka. Thick gorse infestations in the Horton Plains area serve as a habitat for native black lipped lizard and several amphibians in providing food (flowers attract insects) and shade. Gorse stands also provide nesting for birds.

But it is very important to eradicate this isolated gorse patches from Horton Plains before it invade upcountry mountains. This would be an ideal opportunity for the Biodiversity Unit of the Ministry of Environment and Natural Resources to solve this problem before it get out of hand.