The North Harris Trust along with Scottish Natural Heritage are embarking on a project to quantify the extent of Gunnera (Gunnera tinctoria) across the Western Isles. They will then work to produce a plan towards its management and eradication.
Gunnera, commonly known as ‘Giant Rhubarb’ is native to South America and was introduced as an ornamental garden plant. However, it has become an invasive species, taking over gardens and spreading into neighbouring crofts, along roadsides and onto hill land.
Growing to a height of 2m, the large Gunnera leaves shade and out-compete native plants. It can also cause problems by blocking drainage ditches and access tacks. Seeds are spread along water courses and by birds, but also through road building, movement of soil and clearing ditches. Gunnera thrives in our mild, wet climate and is now a major problem in Western Ireland where the climate and landscape is similar to that found in the Outer Hebrides.
Mature Gunnera plants are easily recognisable, in early spring the plant sprouts rapidly from thick sturdy surface roots called rhizomes. Supported by fleshy stems as thick as your wrist and covered in small spikes, the umbrella shaped leaves with spikes on the back can expand to more than a meter across within 3 years. A few photographs are attached to help aid identification.
The Gunnera plant spreads by its root system or rhizomes and entire new plants regenerate from a tiny fragment of broken root. They also disperse by seed, the tiny flowers are borne on erect cone like fruiting heads at the base of the plant.
We are not aware of any Gunnera having established here, but it’s not too far away – there is some growing between Knockiandue and the road end. This is already on the Western Isles database, but please let us know if you have spotted any more.
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