@brightcolours do you know where in particular? I was just thinking it must be in more low lying terrain as they’d get run off or tides in. Maybe it’s too dry here as we are well above sea level. No chance of every being flooded.
“A common garden plant that has become naturalised in damp and shady situations (e.g. in forest margins and along waterways). It is also a weed of roadsides, disturbed sites and waste areas in populated areas.” https://keyserver.lucidcentral.org/weeds/data/media/Html/impatiens_walleriana.htm