Taxonomy

Rhododendron ponticum | Róslabhras

Pre 2017

2017 - 2020

Status

Conservation status

Not Assessed

Legal status

Third Schedule listed species under Regulations 49 & 50 in the European Communities (Birds and Natural Habitats) Regulations 2011. (Note: Regulation 50 not yet enacted).

First reported in the wild

pre-1800

Invasiveness

Invasive species - risk of High Impact

Irish status

Established

Introduction pathways - 1

Release in Nature

Introduction pathways subclass - 1

Landscape/flora/fauna improvement

Invasive score

20

NAPRA Ireland risk assessed

Yes

Species Biology

Identification

Densely branched evergreen shrub, up to 5m tall, leaves 6-20cm in dense terminal racemes, elliptical to oblong, distinctive mauve/purple flowers 4-6cm across (Stace, 1997).

Ecology

Crowds out native plants, forming dense monoculture (Barron, 2007) and impacts on community level processes in streams and rivers where it is present (Hladyz et al., 2011). May produce alleopathic chemicals, preventing native species from growing in soil in which it is present (Hulme, 2009). Hosts a fellow invasive species Phytophthora ramorum (Sudden oak death) which can affect a number of tree species (though not Oak) (Brennan et al., 2008). Control costs in the UK cost ~£560 per ha in 2001 (Dehnen-Schmutz et al., 2004). Honey from bees collecting pollen from Rhododendron may be toxic to humans (Hulme, 2009).

Habitat

Mires, bogs & fens; Grasslands and landscapes dominated by forbs, mosses or lichens; Heath, scrubland & tundra; Woodland, forest and other wooded land; Regularly or recently cultivated agricultural, horticultural or domestic habitat; Constructed, industrial or other artificial habitats; Miscellaneous

Reproduction

Plants set seed at age 12 and can produce over a million seeds per plant (Cross, 1975). Can also spread by layering as branches can root anywhere they touch the ground (Cross, 1975).

Pathway and vector description

Cultivated in Ireland since 1800 (Reynolds, 2002), it is a common garden plant and a wide variety of different Rhododendron breeds and species are sold in Ireland. Spread by seed and layering to its current range.

Mechanism of impact

Competition, Poisoning/Toxicity, Bio-fouling

Broad environment

Terrestrial

Habitat description

Found on a wide variety of habitats, woodlands, peaty and sandy soil, grassland and most suitable places, though rare in urban areas (Reynolds, 2002; Stace, 1997). Generally invades disturbed areas as seedlings have difficulty establishing in areas covered by native plants (Hulme, 2009).

Species group

Plant

Native region

Europe

Distribution

World distribution(GBIF)

Irish distribution

Established - Widespread & Common, Rare in urban areas (Reynolds, 2002).

Native distribution

Rhododendron ponticum is native to a number of regions, Iberia, Turkey, southern Russia and the Lebanon but plants found in Britain are thought to descend from the Iberian populations (Milne & Abbott, 2000).

Temporal change

Date of first record category

Pre-1900

Records submitted to Data Centre in 2019

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How can you help

Report any sightings to the National Biodiversity Data Centre.

Further information

Delivering Alien Invasive Species In Europe (DAISIE) project list rhododendron as one of the 100 Worst Invaders in Europe.

References

Publications

Reynolds, S.C.P. (2002) A catalogue of alien plants in Ireland. National Botanic Gardens. Glasnevin, Dublin. Stace, C. (1997). New Flora of the British Isles 2nd Edition. Cambridge University Press, Cambridge. Dehnen-Schmutz, K., Perrings, C., & Williamson, M. (2004). Controlling Rhododendron ponticum in the British Isles: an economic analysis. Journal of Environmental Management, 70(4), 323-332. Milne, R. I., & Abbott, R. J. (2000). Origin and evolution of invasive naturalized material of Rhododendron ponticum L. in the British Isles. Molecular Ecology, 9(5), 541-556. Cross, J. R. (1975). Rhododendron Ponticum L. The Journal of Ecology, 345-364. Hulme, P. (2009). Rhododendron ponticum L., rhododendron (Ericaeae, Magnoliophyta). In: DAISIE (ed.) The Handbook of European Alien Species. Springer, Dordrecht. Brennan J, Cummins D, Kearney S, Choiseul J, Cahalane G, & Nolan S (2008) Investigating the threat of Phytophthora ramorum to Ireland; the current situation. Phytopathology 98(6 suppl.). Barron, C. 2007. The Control of Rhododendron in Native Woodlands. In: LITTLE, D. (ed.) Native Woodland Scheme Information Note No. 3. Forest Service: Woodlands of Ireland Coillearnacha. Hladyz, S., Åbjörnsson, K., Giller, P. S., & Woodward, G. (2011). Impacts of an aggressive riparian invader on community structure and ecosystem functioning in stream food webs. Journal of Applied Ecology, 48(2), 443-452.

Global Invasive Species Database

DAISIE Factsheet

CABI Datasheet