The Crane Valley Partnership

Key Invasive Species

As with many other rivers in the UK, the River Crane is home to a number of invasive species plant species. They can cause structural damage, increase erosion or create a risk to public health. In addition they can out compete native plant species. The species within the catchment with the greatest need for control are listed below.

Japanese Knotweed

This is a tall, vigorous ornamental plant that escaped from cultivation in the late nineteenth century and has become an aggressive invader within the urban and rural environment. The species is lush green in colour with shovel shaped leaves and a red, hollow stem. It produces white flowers between September and October and can grow as much as 10cm a day.

The plant can cause heave below concrete and tarmac and can subsequently damage buildings and roads.

Himalayan Balsam

This particular invasive was introduced to the UK in 1839 from Northern India. It spreads quickly due to its lack of natural predators and disease and grows in dense stands up to 3m tall. As the plant dies back in late autumn, it leaves bare areas along river banks where it has out competed native plants.  This leaves these areas vulnerable to erosion during the winter rainy season.
Giant Hogweed

A native to the Caucasus Mountains of southwest Asia, giant hogweed was introduced to the UK in 1893. It spreads rapidly due the speed of dispersal of its seeds by water, colonising river banks. The plant’s hollow stems can be 5-10cm in diameter, with raised purple spots and bristles along their length. In summer months it can reach a height of 3-4m when its white, umbrella-like flowers bloom, which can be 70cm in diameter. Giant hogweed can cause human health issues arising from a poisonous sap on the leaves, causing burns and irritation as it comes in contact with skin exposed to sunlight

Floating Pennywort

This is a North American plant introduced to British waterways in 1980 by the aquatic nursery trade. It roots in the shallow margins of slow flowing rivers and forms dense mats of vegetation that rapidly cover the water surface, interfering with both the ecology, morphology and amenity uses of the river. The plant’s leaves can be circular or kidney shaped and can grow to a maximum size of 18mm diameter, extending up to 40cm above the water surface, with its roots extending up to 50cm downwards.