Tomos Jones

Ornamental plants: our future invaders?

The RHS Chelsea survey is now closed. I’ll be sharing some of the preliminary results here soon.

For updates on my RHS Chelsea experience, click here!

I’m a second year PhD student at the University of Reading. I’m a keen gardener, but I originally studied Geography. This combination of geographical and horticultural interest has led to my current PhD research on the invasive potential of ornamental plants; how these plants ‘behave’ in their introduced range and how this might change as a result of climate change. I’m also interested in the role of gardeners in preventing and managing future invasions.

The problem

The RHS Plant Finder contains over 72,000 entries for ornamental plants including many cultivars with features that make then particularly suited to growth in U.K. gardens. This compares with a native flora of 1,500 species in Britain and Ireland. Most ornamental plants have not ‘escaped beyond the garden fence’ and naturalised, and even fewer have become invasive, i.e. have a detrimental ecological impact (Fig.1).

Fig.1: Ornamental plants and the ‘British flora’ (values from Stace and Crawley, 2015)

Ornamental plants are important for wildlife and increase biodiversity by providing ecosystem services such as resources for pollinators. This is particularly true in urban areas. Some research has suggested that a mixture of native and non-native plants can offer an enriched habitat for native insects (Salisbury et al., 2015). One popular example of a non-native plant is Buddleja davidii (Fig.2) which is a great source of nectar for butterflies – giving it its common name Butterfly bush – but it is also invasive.

B. davidii (Tomos Jones)

Gardens constitute a ‘pool’ of ornamental plants which have the potential to naturalise or become invasive in the future; referred to as ‘invasive potential’. This is a particular concern in the context of a changing climate. It is important identify which ornamental plants have naturalisation and/or invasive potential before they become problematic.

Research questions

  1. Which ornamental plants might naturalise in the future, and why?
  2. Which ornamental plants have invasive potential, now and under future climate scenarios?
  3. Can gardeners be effective in identifying invasive potential early in the invasion process?

How can you help?

I’m asking gardeners to help identify future invaders by completing a (very) short survey. This is because gardeners can be the first to observe ornamental plants showing ‘invasive characteristics’ within gardens. Are you a gardener? Please join over 400 gardeners who have already completed the survey.

The plants reported in this survey will feed into species distribution modelling to investigate which plants might find future climate suitable. This will help measure their invasive potential.


Twitter: @TomosJones92


This research is a CASE PhD jointly supervised at the University of Reading and the Royal Horticultural Society under the NERC SCENARIO Doctoral Training Programme.

See also

The RHS Gardening in a Changing Climate report.


Salisbury, A., Armitage, J., Bostock, H., Perry, J., Tatchell, M. and Thompson, K., 2015. Enhancing gardens as habitats for flower-visiting aerial insects (pollinators): should we plant native or exotic species? Journal of Applied Ecology, DOI: 10.1111/1365-2664.12499.

Stace, C.A. and Crawley, M.J., 2015. Alien Plants. London: Harper Collins.