anchor: It might not be the oldest, but Castleton is regarded by many as the  father  of tropical gardens in Jamaica because of its work in the propagation and distribution of new plant genera.
positive: While not the oldest, Castleton is still thought of as the father of tropical gardens in Jamaica because of its distribution of new plants and its work in propagation.
negative: Castleton, the oldest tropical garden in Jamaica, is very obscure and not well known.