Cornwall Wildlife Trust said plants like Japanese Knotweed and Montbretia often spread to the wild from bags of garden rubbish.

Montbretia has become particularly common on Cornwall's roadsides and is pushing out native flowers.

The trust has reminded people about disposing of garden waste responsibly to prevent the spread of these species.

It said people should not throw garden rubbish over hedges or by the roadside as this can introduce alien plants like the montbretia into the wild.

A spokesperson said: "Help protect Cornwall's diverse and colourful displays of native wild flowers by preventing the escape of alien species."