How do gardeners define ‘invasive’? Implications for invasion science and environmental policy instruments on invasive species

Ornamental horticulture is a main introduction pathway for invasive species globally and gardens are a source of potentially invasive species. Gardeners are therefore important actors (i.e. stakeholders) for invasion science and environmental policies on invasive species. Yet, to the authors’ knowledge, no previous study has asked gardeners directly how they define ‘invasive’, and compared this to definitions used within invasion science and environmental policies. For this reason, gardeners were asked to define an ‘invasive’ plant. A deductive approach to thematic analysis of the responses, using key concepts in invasion science and relevant environmental policies, explored the connections between the concepts. This demonstrated the nuanced perceptions and definitions of ‘invasive’ amongst gardeners in Britain, including similarities with how ‘invasive’ is defined especially with the two key concepts of spread and impact. Clear differences were also found; importantly most gardeners only considered the term ‘invasive’ within their gardens (as opposed to the wild). The study also finds that there is better mutual understanding of the term ‘invasive’ between invasion scientists and gardeners than with those involved in environmental policies. Understanding how gardeners define ‘invasive’ has important implications for engaging them with invasion science by exploring the factors determining behaviours in terms of invasive species. This is particularly important in going beyond raising awareness and towards influencing behavioural change more effectively. This study is also relevant to making environmental policies, and especially in their implementation by better knowing how gardeners perceive the issue of invasive species.