Biological management of invasive plants:
Utilising Goats to Keep Old Man’s Beard at Bay in Beaumont Quarry, Cork City

The use of target grazers, such as goats, has been gaining popularity as a management tool for controlling the spread of invasive plants.

Stephanie Corkery May 2023


As a biological control, this has environmental benefits as it eliminates the requirement for harsh chemicals and noisy machinery, that are traditionally employed for common physical and chemical methods of invasive species management.

For the first time in Beaumont Quarry, Cork City, goats are being used as grazers to tackle the invasive plant old man’s beard (Clematis vitalba). The goats are being provided by Billy’s Rent a Goat based in West Cork, which was established to provide an efficient and green solution for tackling scrub overgrowth and the spread of invasive species.

Introduction to Invasive Plant Species

Ornamental trade has been held largely responsible for the introduction of non-native plant species into European habitats. The deliberate introduction of such species may inflict environmental damage and will become an economic burden due to the costly nature of their management and eradication. 1 It is at this stage that a non-native species is classified as an invasive species. In order to become invasive, the invader must survive the transit from its original location and become established at its new site. It must then be persistent in its new environment and have the potential to expand its range to the extent that it diminishes native communities over time.2

Invasive plants are well-known to hinder the growth and community structure of native species, while also contributing to biodiversity loss3 They do this by displacing and competing for space with native species for vital resources integral for their survival. They are also known to be disruptive to various trophic between native species.4 Therefore, the uncontrolled spread of non-native invasive plants poses a significant threat to natural ecosystems on a global scale and is considered to be a major contemporary challenge in the field of ecology [5].5 This has resulted in both ecological and economic implications. For this reason, controlling their spread is a necessary action to take in order to restore the integrity of natural ecosystems. Invasive plant species make their way to new territories through a variety of suitable pathways, also known as vectors. One such vector, as mentioned, includes the import of exotic ornamental species. Others include the accidental introduction via a variety of human activities.

That said, a relatively small proportion of deliberately introduced plant species will come to have a detrimental effect on indigenous plant communities. This has been estimated to be as low as 1% in some cases [6]6. Additionally, Ireland for example, has a relatively small number of invasive plant species despite up to a third of its naturalised species being classified as non- native [7]7.

Many management strategies exist for controlling invasive plants. The most effective approach is determined by factors such as the species in question, the financial capacity of the responsible authority, and the respective national legislation permits regarding pest management [8]8. Methods of control of invasive plant species include chemical controls, physical/ mechanical controls, in addition to biological controls [9]9. Of all the control measures discussed, biological control is considered to be the ideal approach due to its low cost and minimal impact on the environment as it employs the natural interactions between different species [10]10.

Due to the benefits of using grazing animals to combat the spread of invasive plant species, goats will be employed in Beaumont Quarry as a means to control the spread of old man’s beard (Clematis vitalba). This will be run by Billy’s Rent a Goat in collaboration with Cork Nature Network in the summer 2023

Old Man’s Beard at Beaumont Quarry

Old man’s beard (Clematis vitalba), also referred to as traveller’s joy, is a deciduous perennial native to central and southern Europe, in addition to parts of Asia including Georgia, Iran, and Syria. This species has also been introduced to Australia, New Zealand, and North America [11]11.

In terms of appearance, the stems of an old man’s beard (Figure 1) may vary in colour, ranging from green to dark purple, and can become twisted around suitable objects. This includes trees and fences. Stems can measure approximately 15 to 20 cm in diameter. The leaves are distinctively or heart-shaped in appearance. This species also flowers, however these often do not develop until its third year.

Figure 1: Old man’s beard (Clematis vitalba). Source: Irish Wildflowers.

Old man’s beard was originally introduced to Ireland as an ornamental garden plant but has since escaped into the natural environment where it has become an invasive species, particularly in the southern portion of the country [7], [12]712. It is known to invade a variety of habitats such as agricultural grasslands, wastelands, open spaces, roadsides and forest edges, and is considered to be an invasive species of Medium Impact [13]. Additionally, it is found growing in hedgerows and along roadsides in alkaline soils [7]. It successfully invades habitats by being able to reproduce both via seed, and vegetative growth via stem fragmentation.

Beaumont Quarry is an abandoned limestone quarry located to the southeast of Cork City centre, in Ballintemple (Figure 2). Due to its location, Beaumont Quarry is considered to be a significant hub for Cork’s urban wildlife. The area is comprised of calcareous grasslands and is characterised by mineral-rich, shallow soils. Approximately 154 plant species have been recorded in Beaumont Quarry as of 2021 [14].

Figure 2: Beaumont Quarry location. Source: Cork Nature Network.

Beaumont Quarry, however, faces several ecological threats, one being the presence of invasive plants. Examples of such species present include Japanese knotweed (Fallopia japonica), winter heliotrope (Petasites pyrenaicus), as well as old man’s beard. Non-native scrub removal has been and continues to be, carried out to slow its impact on the calcareous grassland.

Since 2015, Cork Nature Network (CNN) has been working in Beaumont Quarry alongside Cork City Council and Beaumont Local Residents Committee with the common goal of conserving wildlife, carrying out research, and educating the public on urban wildlife. CNN developed a management plan for the quarry for 2022 to 2027. A new initiative for 2023 is to biologically control the spread of old man’s beard using grazing goats.

Figure 3: Beaumont Quarry. Source: Cork Nature Network

Goats as a Tool to Manage Invasive Species

Grazing by large-bodied domestic herbivores has been proven to be effective in suppressing certain species of invasive plants. Such herbivores include cows, horses, sheep, and goats [15].

There has been a steady increase in the use of goats (Capra hircus) as target grazers to manage invasive plant species. One organisation employing this method is Billy’s Rent a Goat, based in West Cork. Billy’s Rent a Goat was established by William Walsh as an environmentally friendly and natural solution to clear wasteland and invasive plant species without the requirement for toxic chemicals or heavy machinery [15]. Billy’s Rent a Goat uses mainly rescued male goats as an efficient and green solution for tackling scrub overgrowth and the spread of invasive species.

There are many benefits of using goats and other herbivores to manage invasive plants. These include clearing the land without causing any pollution, a reduction in the need for chemical fertilisers that add toxins to the soil, and heavy machinery. Additionally, this method will produce less noise and odour. Over time, goats will restore the ecological balance to the landscape in question. Goats will also fertilise the land as they work it while sterilising weed seeds.

This approach of biological control has been employed already in Cork by Billy’s Rent a Goat which involved the removal of wasteland to make way for a wildflower meadow at a site in Turner’s Cross school, Cork City [16].


  1. Clewley, G.D., Eschen, R., Shaw, R.H., Wright, D.J. (2012). The effectiveness of classical biological control of invasive plants. Journal of Applied Ecology49, 1287-1295
  2. Jeschke, J.M., Keesing, F., Ostfeld, R.S. (2013). Novel Organisms: comparing invasive species, GMOs, and emerging pathogens. AMBIO42, 541–548.
  3. Brancatelli, G.I.E., Zalba, S.M. (2018). Vector analysis: a tool for preventing the introduction of invasive alien species into protected areas. Nature Conservation, 24, 43-63.
  4. Martijn Bezemer, T., Harvey, J.A., Cronin, J.T. (2014). Response of Native Insect Communities to Invasive Plants. Annual Review of Entomology59, 119-141.
  5. Carpenter, D., Cappucinno, N. (2005). Herbivory, time since introduction and the invasiveness of exotic plants. Journal of Ecology93, 315-321.
  6. Williamson, M. (1996). Biological Invasions. Chapman & Hall, London.
  7. Reynolds, S.C.P. (2002). A catalogue of alien plants in Ireland. Glasnevin. National Botanic Gardens.
  8. Weidlich, E.W.A., Flórido, F.G., Sorrini, T.B., Brancalion, P.H.S. (2019). Controlling invasive plant species in ecological restoration: A global review. Journal of Applied Ecology57, 1806-1817.
  9. National Biodiversity Data Centre. (2021). Control and Management: Guiding principles on control and management. Available at: Control and Management – [Accessed 15 May 2023]
  10. Urban, A.J., Simelane, D.O., Retief, E., Heystek, F., Williams, H.E., Madire, L.G. (2011). The invasive ‘Lantana camara L.’ hybrid complex (Verbenaceae): A review of research into its identity and biological control in South Africa. African Entomology19, 315–348.
  11. Ogle, C. C., La Cock, G. D., Arnold, G., & Mickleson, N. (2000). Impact of an exotic vine Clematis vitalba (F. Ranunculaceae) and of control measures on plant biodiversity in indigenous forest, Taihape, New Zealand. Austral Ecology25, 539-551.
  12. Department of Agriculture, Food and the Marine. (n.d.). Invasive Plant Information Note: Old Man’s Beard (Clematis vitalba). Available at: 79144_d9734bdb-24af-44f1-bfb0-b3dc363c2aec.pdf [Accessed 15 May 2023]
  13. National Biodiversity Data Centre. (n.d.). Clematis vitalba | Traveller’s-joy | Gabhrán. Available at: Species Profile Browser · Species Profile ( [Accessed 15 May 2023]
  14. Cork Nature Network. (2022). Beaumont Quarry. Available at: Beaumont Quarry | Cork Nature Network [Accessed 15 May 2023]
  15. Esselink P, Zijlstra W, Dijkema KS, Van Diggelen R. (2000). The effects of decreased management on plant- species distribution patterns in a salt marsh nature reserve in the Wadden Sea. Biological Conservation, 93, 61-76.
  16. Billy’s Rent a Goat. (2021). Available at: Billy’s Rent a Goat – Billy’s Rent a Goat – Clear your land with friendly goats – [Accessed 10 May 2023]
  17. Dunphy, L. (2021). Watch: The goats let loose – Rescued animals to clear Cork school’s wasteland. Available at: Watch: The goats let loose – Rescued animals to clear Cork school’s wasteland ( [Accessed 15 May 2023]
Stephanie Corkery
+ posts
1. Clewley, G.D., Eschen, R., Shaw, R.H., Wright, D.J. (2012). The effectiveness of classical biological control of invasive plants. Journal of Applied Ecology, 49, 1287-1295
2. Jeschke, J.M., Keesing, F., Ostfeld, R.S. (2013). Novel Organisms: comparing invasive species, GMOs, and emerging pathogens. AMBIO, 42, 541–548. ↩︎
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