Botanic Gardens Conservation International (BGCI) is a leading conservation organisation linking and representing botanic gardens across the world. Established in 1987 it has pioneered the ‘Red Listing’ process to discover and report on the state of native plant populations. You can read more about their work here www.bgci.org/
Rhododendron, Camellia and Magnolia are genera with dedicated Red Lists which are available for download below.
In addition, Rhododendron and Magnolia benefit from published ex-situ surveys, works which the species element of our Extant Plants Databases of plants cultivated in the UK serves to complement and inform.