Researcher identifies windmill palm and Argentinian vervain as potential invasive species

Windmill palms, muscari and verbena bonariensis (Argentinian vervain) are three plants among 30 that University of Reading researchers believe could have a future impact on the UK countryside.

The University's Chelsea flower show discovery zone exhibit showed 'future invaders' that threaten native biodiversity. Monbretia and gunnera are examples of plants that have escaped into the wild.

There are only 1,500 native plants in Britain and Ireland but UK gardens are home to over 76,000 different ornamental plants. In the UK there are 17,000 species in the RHS plant finder, 1,080 ornamental plants that have escaped into the environment, and 52 invasive species.

Some introductions have become invasive, such as Himalayan balsam and Giant hogweed. Verbena bonariensis is a very commonly used landscaping and garden design plant but has the attributes to be able to naturalise into the British environment.

The exhibit included plants known to be invasive, such as Buddleia davidii (Butterfly bush) and Lamium galeobdolon subsp. argentatum (Yellow archangel), as well as the potential invaders. The architectural leaves of Giant rhubarb were the inspiration for the exhibit.

Alchemilla mollis (Lady's mantle), Houttuynia cordata (Heart-leaved houttuynia) and Trachycarpus fortunei (Chinese windmill palm) are not regarded as invasive but are being put forward as potential future invaders by PhD student Tomos Jones

The work is part of a NERC SCENARIO project at the University, led by Jones with help from Dr Alastair Culham. The exhibit at RHS Chelsea was a collaboration between the Schools of Architecture, Biological Sciences and Arts and Communication Design at the University.

Culham said: "People think gardens are just gardens but they are part of the wider environment. A lot of these plants get out of gardens. Even Japanese knotweed was once sold as an ornamental plant."

He added that the number of species that have escaped from gardens into the wild will exceed the number of natives species in the UK at some point in the future.

Culham said a Swiss study had shown the Chinese windmill palm grew well in the Swiss environment and that means it could grow well here, potentially popping up in Cornish oak forests. He said many of the 30 species did not support many UK insects, as a tree such an an oak does, though they may benefit bees and butterflies with their nectar. They may also displace natives too.


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