There’s a climbing vine in my garden which has hydrangea-like flowers. I have lost the tag, and don’t know if it is Hydrangea petiolaris, or Schizophragma hydrangeoides–how can I distinguish one from the other?
There is an article in Arnoldia (the journal of the Arnold Arboretum at Harvard University) from July 24, 1933 which explains that the two plants are related, but the flower ‘petals’ (which are actually sepals) surrounding the center are distinct:
“In Hydrangea petiolaris this encircling tiara is composed of greenish white flowers, each one made up of four rounded sepals. In Schizophragma hydrangeoides these showy sepals are a purer white and they are borne singly rather than in fours.”
University of Arkansas Extension also says that Schizophragma “differs in flowering time (after climbing Hydrangea) and in the fact that it protrudes less from structures.”
There is another less commonly grown climbing Hydrangea, Hydrangea integrifolia, an evergreen that grows to 40 feet tall and 20 feet wide. Its flower buds look almost like those of peonies, and its leaves are elongated and glossy.