petition at the bottom of this article TO PROHIBIT
the sale of invasive species in Ireland.
Groundwork was established by students in 1981 to tackle the Rhododendron infestation in Killarney National Park. These volunteers coordinated sweeping exercises across 40-acres for 3-months of the year to remove shrubs and new saplings.
In 2010, after 30-years of successful treatment and removal, the NPWS began refusing Groundwork’s assistance. Choosing to rely instead on contractors, dedicated rangers and international volunteers.
Subsequently, there has been a significant and rapid re-infestation of the park. According to Groundwork, the NPWS are in breach of the Habitats Directive as no management plan has been implemented to address the problem.
Groundwork made a formal complaint to the European Commission in 2014, which was initially closed as there was an ongoing review for mismanagement in the wider catchment. However, it was discovered that sections of Killarney National Park have been in continuous forestry for up to 10,000 years. In light of this fact, and the rarity of ancient Irish woodlands, the case was reopened and is ongoing.
Last year the European Court of Justice (ECJ) ruled that the Irish Government had “generally and persistently failed” to protect Irish habitats, not just in the Macgillycuddy Reeks, but across the island. They noted that after 20-years of funding, “many [conservation] sites had no conservation measures at all”.
Rhododendron and Cherry Laurel are, according to the NPWS, the “greatest threat to our remaining native woodlands”. One could argue that efforts to plant new native forests are wasted if we do not address these invasive species.
Beneath the vaulted arches of the trees, tiered flora, from the herbs to the flowers and shrubs, provide the matrix to support a complex ecosystem. These two pervasive non-native species, introduced as ornamental plants, are currently destroying this biodiversity. The fact that both can be bought in Garden Centres, and that experienced volunteers are being turned away, highlights the inconsistency of our approach.
These problems began with English landscape gardening, which was a naturalistic response to the sophistication of Versailles in the 18th century. Decorative temples were built to crown hills and picturesque ruins were carefully constructed to create a tamed ‘naturalness’. On some estates, people were even paid to dress as druids and live in hermitages for the entertainment of the Aristocracy.
Within this elitist gardening culture, the Rhododendron, with its exquisite bell-shaped flowers, was introduced to Ireland. Its popularity increased as new varieties were discovered, notably by Irish-botanist Augustine Henry on his 19-year botanical escapades in the Far East.
The Rhododendron likes mild, moist conditions with acidic soil and is extremely hardy. They have multiple, highly successful methods of reproduction, including self-replication: if a branch dips below the surface, or is covered in dirt, it will begin to form new roots. A single flower can also disperse between 3,000-7,000 seeds up to 1km away with the wind.
Once they take root, they begin to grow into dense thickets of evergreen leaves that cast a permanent shadow where nothing else can live. During their rise to domination, grazing animals avoid their poisonous leaves which grants them a significant advantage over native species.
Their leaf litter is believed to inhibit the recolonisation of other seeds by acidifying the soil, reducing cation exchange. Very few Irish insects are associated with Rhododendron as they haven’t evolved together; subsequently, bird populations drop around infestations.
Rhododendron can carry a fungus-like pathogen called Phytophthora Ramorum which has over 100 types. One of which caused the destruction of 18,000ha of larch between 2010-2016; another has earned the ominous name: ‘Sudden Oak Death’.
The Elizabethian’s introduced Cherry Laurel from Turkey in the 16th century to enjoy the glossy foliage and purple-black summer berries. In isolation, the branches of the laurel will grow lazily upwards to a height of up to 8m. Planted in rows, they weave an impenetrable barrier of evergreen leaves that makes exceptional hedging.
Laurel prefers fertile old woodland soil and is especially pervasive in lowland woodland pasture and parkland, where it spreads pervasively and eradicates all herbaceous and shrub layering plants. They are avoided by herbivory wildlife and outcompete native species by suppressing regeneration beneath their evergreen leaves. Laurel also spreads by layering and suckering, but the fruit may also be eaten and dispersed by birds.
Cherry Laurel is currently destroying the ancient Hazelwood Forest of Sligo. Coillte removed 26 acres of laurel between 2005 and 2009; an additional 30 acres have just been assigned with the Seeds for Nature plan. Their methodology involves chipping the biomass and killing the stumps with herbicide using the ‘drill and drop’ method.
Due to the tenacity of these plants, not a single branch is allowed to remain, otherwise, it may grow roots within a few weeks. Herbicide is used to kill the roots or it will regenerate and flower within 4 years. However, this liquid death is not allowed within 15m of a river so there is currently no treatment along our waterways which puts them in a precarious position.
Laurel loves rivers, which can be seen in the Massy Estate in South Dublin and the Glen of the Downs Nature Reserve. The only available treatment is stump removal, which is highly disruptive to the river bank and risks sedimentation and the entombment of fish spawning beds.
Together, Rhododendron and Cherry Laurel have now invaded three protected habitats in Ireland, upland oak woods, bogs and heath, compromising the future survival of these habitats.
Cherry Laurel and Rhododendron continue to spread despite great efforts and will destroy our native forests unless things change. These plants have already spread across the island and their growth is so pervasive that isolated efforts are futile.
Market development for this biomass is needed to incentivise nationwide removal. The biomass should be sent to sawmills or used as an alternative to peat for home heating. Burning wood may sound like a contentious topic, however, as over 40% of homes in the midlands burn turf for home heating, Cherry Laurel could be a viable alternative.
Shockingly, there are no specific legal provisions associated with the growing of Rhododendron or Cherry Laurel on the island of Ireland and they’re often found for sale in garden centres. It is a tragedy that with efforts to enhance the natural beauty of our gardens we’re contributing to the destruction of our remaining woodlands.
We need to establish a standard: Rhododendron and Cherry Laurel have no place in a respectable garden and their sale must be banned on the island. We’ve begun a PETITION which will be sent to the Oireachtas Joint Committee on Public Petitions. Please sign below and share this article.
The Gaelic Woodland Project has also applied for a grant from the Local Authorities Waters Programme to experiment with mycelium (fungi) as a nature based alternative to herbicide. Our hope is that by inoculating stumps with facultative saprophyte fungi, such as Honey Fungus, we can impede or even prevent regrowth.
This could present a new Best Practice for treatment of infected riverbanks. We will observe the efficacy of this bio-herbicide in the Kilyon Manor Estate, Meath, where Cherry Laurel is threatening the River Deel: a Special Area of Conservation.
We will publish our findings in a methodology for community action against invasive species and endeavour to explore market chain development for the biomass to incentivize it’s removal.
- Irish Wildlife Trust: Groundwork complains to the European Commission for lack of management at Killarney National Park Link.
- Coillte: Works Begin Again To Clear Rhododendron In Hazelwood Forest Link.
- Research: RHODO: Achieving Effective Rhododrendron Control Link