The hop hornbeam is displaying its papery seed pods beside the South Walk.
A member of the birch family (Betulaceae) Ostrya carpinifolia, or the hop hornbeam, is one of ten species of deciduous trees from Europe, Asia, North America and Central America. They all have alternate leaves, and flowers held in catkins, and the female catkins develop to produce attractive hop-like fruits. They are closely related to the hornbeams (Carpinus), but differ in producing the papery, bladder-like husks which protect the seeds. The foliage of this species closely resembles that of the hornbeams, hence the specific name carpinifolia. Growing to 20m in height O. carpinifolia is as wide as it is tall, and grows to produce a rounded canopy. It is a native of south eastern Europe, Turkey and the Caucasus.