What is the rarest and or most endangered plant on the earth?

Question

Subquestions:
1)Found in endemic or wild surrounding.
2)In botanical gardens or collections.
3)What is the rarest sample of any plant, alive or dead?

Answer 1

the world's rarest plant is arguably Encephalartos woodii, a cycad, of which only one specimen has ever been found growing wild in South Africa. it has disappeared and the species now only exists in botanical gardens