It is generally accepted that Rhododendrons are native to the shores around the Black Sea and were introduced to Britain in the mid 18th century for its a blaze of colour during early summer but the shrub was actually part of the British flora before the last ice year.
In my posting a few days ago about oak trees I linked to a study listing the number of insect species associated with various British shrubs. The oak came top out of the 30 shrubs and trees listed with 284 species of insect. Guess how many species are associated with the Rhododendron?
A clue: it came bottom of the list.
This answer is none. Nil, …zero, …zilch.
Conservation bodies agree that Rhododendrons are an invasive species, crowding out native flora, and undertake programmes to control its spread.