Waterborne spread of introduced plants from a large ornamental garden in northern England, UK
DOI:
https://doi.org/10.33928/bib.2026.08.084Keywords:
garden escapes, hydrochory, introductions, invasive, naturalised, watercoursesAbstract
The spread of non-native plants from ornamental gardens is an introduction pathway that has rarely been studied in detail. Here we document the escape of garden plants along a riparian corridor below a large ornamental garden in northern England. Of the 42 naturalised garden escapes found, 14 had originated from the garden itself including two species that were locally invasive (Cardamine bulbifera, Lysichiton americanus). Along with the ubiquitous Impatiens glandulifera, C. bulbifera was the most abundant non-native and had spread by bulbils to form dense stands on sandy riverbanks disturbed by winter floods whereas L. americanus had spread by seed to form dense stands in swampy woodland. All other non-natives were locally distributed. These findings highlight the important role that ornamental gardens play as ‘entry points’ for non-native plants and emphasises the need for gardens to identify, manage and in some cases eradicate potentially invasive species, especially where they have the potential to escape and spread along watercourses.
References
Atkinson, M.D. & Atkinson, E. 2020. Biological Flora of the British Isles, No. 293: Lathraea clandestina. Journal of Ecology 108:2145–2168.
Braithwaite, M.E. 2014. A Short Flora of Berwickshire. Clarilaw: privately published.
Coakley, S. & Petti, C. 2021. Impacts of the invasive Impatiens glandulifera: lessons learned from one of Europe’s top invasive species. Biology 2021, 10, 619. https://doi.org/10.3390/biology10070619.
Corner, R.W.M. 1996. Arenaria balearica L. (Mossy Sandwort): observations on waterborne spread in Perthshire. Watsonia 21:200202.
Culley, T.M., Dreisilker, K., Ryan, M.C., Schuler, J.A., Cavallin, N., Gittig, R., Havens, K., Landel, H. & Shultz, B. 2022. The potential role of public gardens as sentinels of plant invasion. Biodiversity & Conservation 31:18291844.
Davie, J.H. & Akeroyd, J.R. 1983. Pachyphragma macrophyllum (Hoffm.) Busch (Cruciferae), a Caucasian species naturalised in County Avon, England. Botanical Journal of the Linnaean Society 87:77−82.
Hejda, M. & Pyšek, P. 2006. What is the impact of Impatiens glandulifera on species diversity of invaded riparian vegetation? Biological Conservation 132:143−152.
Hulme, P.E. 2011. Addressing the threat to biodiversity from botanic gardens. Trends in Ecology and Evolution 26:168174.
Hulme, P.E. 2014. Resolving whether botanic gardens are on the road to conservation or a pathway for plant invasions. Conservation Biology 29:816824.
Hulme, P.E. & Bremner, E.T. 2006. Assessing the impact of Impatiens glandulifera on riparian habitats: partitioning diversity components following species removal. Journal of Applied Ecology 43:43−50.
Kent, D.H. 1956. Senecio squalidus L. in the British Isles. Proceedings of the Botanical Society of the British Isles 2:115.
Lacey, W.S. 1957. A comparison of the spread of Galinsoga parviflora and G. ciliata in Britain. In: J.E. Lousley, ed. Progress in the Study of the British Flora, pp.109115. Botanical Society of the British Isles Conference Reports, Number 5. London: BSBI.
Manson, D.C. 2004. Cardamine bulbifera in Harrogate. BSBI News 97:22.
Rich, T.C.G. 1991. Crucifers of the British Isles. Botanical Society of the British Isles Handbook Number 6, London: BSBI.
Rodwell, J., ed. 1991. British Plant Communities. Volume 1. Woodlands and Scrub. Cambridge: Cambridge University Press.
Ronse, A. 2011. ‘Botanic garden escapes’ from the living collections at the Botanic Garden. Scripta Botanica Belgica 47:89111.
Sanderson, N.A. 2013. Research on the impact of American Skunk Cabbage Lysichiton americanus on native vegetation. Report commissioned by Hampshire & Isle of Wight Wildlife Trust on behalf of The New Forest Non-Native Plants Project.
Showler, A. & Rich, T.C.G. 1993. Cardamine bulbifera (L.) Crantz (Cruciferae) in the British Isles. Watsonia 19:231−245.
Stace, C.A. 2019. New Flora of the British Isles. 4th. ed. Middlewood Green, Suffolk: C & M Floristics.
Stace, C.A. & Crawley, M.J. 2015. Alien Plants. New Naturalist 129. London: Harper Collins.
Stroh, P.A., Walker, K.J., Humphrey, T.A., Pescott, O.L. & Burkmar, R.J. 2023. Plant Atlas 2020. Mapping Changes in the Distribution of the British and Irish Flora. 2 volumes. Princeton: Botanical Society of Britain and Ireland & Princeton University Press.
Wadsworth, R.A., Collingham, Y.C., Willis, S.G., Huntley, B. & Hulme, P.E. 2000. Simulating the spread and management of alien riparian weeds: are they out of control? Journal of Applied Ecology 37:28–38.
Wallace, I. 2005. Cardamine bulbifera (Coralroot) in Harrogate. BSBI News, 98:35.
Walker, K.J. 2009. Water-borne dispersal of Cardamine bulbifera (L.) Crantz (Brassicaceae) in Mid-west Yorkshire (v.c. 64). Watsonia 27:250253.
Walker, K.J. 2017. Pachyphragma macrophyllum (Hoffm.) Busch (Caucasian Pennycress) naturalised by streamsides in Yorkshire (v.c.64). BSBI News 135:7576.
Walker, K.J. 2021. The rare plants of the HDNS area: Yellow Star-of-Bethlehem Gagea lutea. Harrogate District Naturalists’ Society Report for 2018: 15−20.
Weiblen, G.D. & Brehm B.G. 1996. Reproductive strategies and barriers to hybridization between Tellima grandiflora and Tolmeia menziesii (Saxifragaceae). American Journal of Botany 83:910–918.
Zhang, L. 1983. Vegetation ecology and population biology of Fritillaria meleagris L. at the Kungsängen Nature Reserve, Eastern Sweden. Acta Phytogeographica Suecica 73:1−96.
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