Many woodlands and park areas across Ireland are under demise due to the presence of invasive alien plants. In this guest blog, Heritage Officer Melanie McQuade outlines the response Westmeath County Council have taken to deal with the invasion at the Belvedere House, Gardens and Park site.
Belvedere House, Gardens and Park is an important Heritage site in Westmeath, where the 18th Century designed landscape adjoins Lough Ennell Special Area of Conservation (SAC), Special Protection Area (SPA), proposed Natural Heritage Area (pNHA).
As many as eleven different plants now recognised as Invasive Alien Plant Species have been identified at Belvedere, where they would originally have been planted as ornamentals and/or as ground cover for game. These species are Bohemian knotweed (Reynoutria bohemica), Giant knotweed (Reynoutria sachalinensis), Himalayan knotweed (Koenigia polystachya), Japanese knotweed (Reynoutria japonica), American skunk cabbage (Lysichiton americanus), Buddleja (Buddleja davidii), Cherry laurel (Prunus laurocerasus), Gunnera (Gunnera tinctoria), Rhododendron (Rhododendron ponticum), Traveller’s joy (Clematis vitalba), and Winter heliotrope (Petasites pyrenaicus).
The distribution and density of these species varies from rare to widespread and from occasional to dominant. The three most abundant species of concern are Knotweed, Cherry Laurel and Rhododendron. They have spread to such an extent that they have outcompeted other plant species and are having a detrimental impact on the woodland dynamics and biodiversity of the site.
Given the scale of the issue, Westmeath County Council engaged Invas Biosecurity Ltd to prepare a Management Plan for Invasive Alien Plant Species at Belvedere Gardens and Park.
The Plan, which was prepared in 2020 with funding from the National Biodiversity Action Plan Grant Scheme from the NPWS, is a multi-annual plan for managing these Invasive Alien Plant Species. The long-term impact of implementing this Plan will be to reduce the hold of Invasive Alien Species and to help restore biodiversity within the Parklands.
In early September 2020, all locations of Japanese Knotweed were treated with herbicide. In most locations this was done by spraying but stem injection was the method used for plants on or near a water course. The effect of treatment was clear in 2021 and further treatment was carried out in the Autumn. The Knotweed will be treated again in 2022.
Cherry Laurel is the most widespread species of concern at Belvedere and in a sizable area of the Park it has become dominant (i.e. comprising over 70% of ground cover). This dominance of Cherry Laurel is due in part to the cyanide-based chemicals it deposits into the soil which inhibit other trees from growing. Its evergreen leaf cover also creates dense shade which further inhibits natural regeneration by other tree species.
Three areas of Cherry Laurel (measuring c.5,300m2 in total) were cleared in 2021 by felling, treating stumps and mulching branch material. Cut logs were removed from site.
All work was carried out by appropriately trained personnel, in line with best practice and according to methodologies set out in the Management Plan. This was especially important where the Invasive Alien Species are growing near water courses and in the area adjoining Lough Ennell, which is a Special Area of Conservation (SAC) and a Special Protection Area (SPA).
In conjunction with the management of these species, Ecologists Flynn Furney were engaged to provide training in the identification and management of Invasive Alien Plant Species for Westmeath County Council Outdoor Staff. The Ecologists had hoped to provide onsite information sessions on Invasive Alien Plant Species for members of the public, but given the on-going restrictions around Covid-19, it was decided that an online presentation would be more appropriate. The presentation provided an introduction to and discussion about all invasive alien plant species of concern, not just those growing at Belvedere https://www.youtube.com/watch?v=QicTanbBCus&t=3s
Funding from the National Biodiversity Action Plan Grant Scheme from the NPWS and from the Heritage Council is gratefully acknowledged. This funding enabled the implementation of the Management Plan for Invasive Alien Species at Belvedere in 2021.
Now that a considerable area has been cleared of Cherry Laurel, there is an opportunity to plan some planting. Native, pollinator friendly tree species have been kindly sponsored by Peter Cuthbert. These tree saplings will be planted in early 2022.
