Rhododendron

Not a native plant for Scotland, but an import in the 18th century for decorative purposes that has been too successful at establishing itself.

The shrub’s dense foliage means little else can grow alongside it, meaning there is little sustenance left for native wildlife, and it poisons the soil, preventing the growth of other plants. Once it takes over the lower storey of a wood, new tree seedlings cannot get established because they have no light. In time the older woodland trees will die, leaving the rhododendrons triumphant.