Stuck on this - feel I should know but haven't a clue.

"Climbing plant or tree of tropical and warm regions named after two
french herbilists"

8 letters Blank A blank H blank N blank blank , not criptic.

I have done the rest but I can not find it
--
Charlie Pridham, Gardening in Cornwall
www.roselandhouse.co.uk
Holders of national collections of Clematis viticella cultivars and
Lapageria rosea