Rhododendron (Rhododendron ponticum) is an established non-native invasive species within the UK, threatening a variety of habitats and the associated flora and fauna.  Rhododendron ponticum and the hybrid Rhododendron ponticum x Rhododendron maximum are listed under Schedule 9 to the Wildlife and Countryside Act 1981 with respect to England and Wales. As such, it is an offence to plant or otherwise allow this species to grow in the wild.
Potentially toxic chemicals, particularly 'free' phenols, and diterpenes, occur in significant quantities in the tissues of Rhododendron ponticum. Diterpenes, known as grayanotoxins, occur in the leaves, flowers and nectar.