Reed Canary Grass: Ecology, Impacts, and Insights

Reed canary grass Phalaris arundinacea, a tall, perennial grass, is a familiar sight across Britain’s wetlands and waterways. While native to Europe, including the UK, this species has become a management challenge due to its aggressive growth and potential invasiveness. In this blog post, we’ll explore its habitat requirements, associated vegetation communities, the ecological communities it supports, its role as a food plant, and its invasive potential in Britain, drawing on scientific literature for a comprehensive understanding.

Reed canary grass growing in a typical wet grassland habitat along a ditch side.

Habitat Requirements in Britain

In Britain, reed canary grass thrives in wet, nutrient-rich environments such as marshes, fens, riverbanks, ditches, and floodplains. It prefers soils that are waterlogged or saturated for much of the growing season, though it can tolerate drier conditions in disturbed or shaded areas. Its ability to withstand prolonged flooding makes it a dominant species in lowland wetlands and along canals. The grass benefits from nutrient enrichment, often linked to agricultural runoff or urban pollution, and disturbances like dredging or land drainage enhance its spread.

A study by Lavergne and Molofsky (2004) notes that P. arundinacea excels in altered hydrological regimes, common in Britain’s heavily managed waterways. Its rhizomatous growth forms dense mats, allowing it to outcompete other species in these dynamic habitats. In the UK, it is particularly abundant in lowland areas, such as the Somerset Levels and the Norfolk Broads, where wet conditions and human activity create ideal conditions.

Associated Vegetation Community

In Britain’s native wetland ecosystems, reed canary grass naturally occurs alongside species like common reed Phragmites australis, sedges Carex spp., and forbs such as meadowsweet Filipendula ulmaria and marsh marigold Caltha palustris. In less disturbed fens and wet meadows, it integrates into diverse plant communities. However, in areas affected by nutrient enrichment or hydrological changes, P. arundinacea often forms dense, monospecific stands that suppress native vegetation.

Research by Wheeler and Shaw (1991) highlights that in British fens, high nutrient levels can shift plant communities toward dominance by aggressive species like reed canary grass, reducing biodiversity. Its thick thatch and shading effect limit the growth of smaller plants, creating near-monocultures in heavily impacted sites, such as agricultural ditches or urban wetlands.

Ecological Community Supported

Reed canary grass supports a range of wildlife in Britain, though its ecological value is context-dependent. In floodplain and wetland habitats, it provides cover for birds, small mammals, and invertebrates. For example, species like the reed bunting Emberiza schoeniclus and water vole Arvicola amphibius may use its dense stands for nesting or shelter. However, its tendency to form monocultures can reduce habitat diversity, negatively affecting species that rely on varied plant communities.

In urban wetlands, such as those in London or Manchester, P. arundinacea can play a surprising role. A study by Gledhill et al. (2008) suggests that in degraded urban ponds, reed canary grass provides habitat for amphibians like the common frog Rana temporaria and common toad Bufo bufo, offering cover from predators and supporting tadpole survival. Yet, in high-quality fens or wet meadows, its dominance often degrades habitat for specialist species, such as rare orchids or invertebrates dependent on diverse vegetation.

Can It Become Invasive in Britain?

Although native to Britain, reed canary grass can exhibit invasive behaviour, particularly in disturbed or nutrient-enriched habitats. Its rapid spread via rhizomes and seeds, combined with its tolerance of a wide range of conditions, allows it to dominate wetlands, ditches, and riverbanks. In the UK, it is considered a management concern in conservation areas, such as Sites of Special Scientific Interest (SSSIs), where it can outcompete rare native plants and reduce biodiversity.

The grass’s invasiveness is exacerbated by human activities, including land drainage, agricultural intensification, and the introduction of non-native cultivars for erosion control or forage. Genetic studies suggest that some British populations may include hybrid or introduced genotypes, increasing their vigour (Lavergne and Molofsky, 2004). In areas like the Cambridgeshire Fens, dense stands of P. arundinacea have been linked to declines in native fen species.

Control measures in Britain include mowing, grazing, herbicide application (e.g., glyphosate), and hydrological restoration to reduce nutrient levels. The Environment Agency and conservation groups, such as the Wildlife Trusts, recommend integrated management to suppress P. arundinacea while encouraging native species. However, its persistent seed bank and rhizomes make eradication challenging, often requiring years of sustained effort.

Conclusion

In Britain, reed canary grass is a native species with a dual identity: a natural component of wetland ecosystems and a potential invader in disturbed habitats. Its ability to thrive in nutrient-rich, wet environments makes it a common sight along rivers, canals, and urban ponds, where it supports some wildlife, like amphibians and birds, but often at the cost of biodiversity. Its aggressive growth threatens high-value conservation sites, necessitating careful management to balance its ecological roles with the need to protect native flora and fauna.

By understanding P. arundinacea’s ecology through scientific research, land managers and conservationists in Britain can develop effective strategies to mitigate its impacts while preserving its native contributions. Whether you’re exploring a fen in East Anglia or a ditch in the West Midlands, reed canary grass offers a compelling glimpse into the challenges of managing dynamic wetland ecosystems.

References

• Gledhill, D. G., et al. (2008). Urban wetland ecology and management in the UK. Freshwater Reviews, 1(2).

• Lavergne, S., & Molofsky, J. (2004). Reed canary grass (Phalaris arundinacea) as a biological model in the study of plant invasions. Critical Reviews in Plant Sciences, 23(5).

• Wheeler, B. D., & Shaw, S. C. (1991). The impact of nutrient enrichment on fen vegetation. Journal of Applied Ecology, 28(3).

• Natural England. (2020). Management of reed canary grass in wetland SSSIs.

• Environment Agency. (2019). Invasive species management guidelines for UK waterways.