a family of dicotyledonous plants in-including small trees or shrubs, lianas, undershrubs, and grasses. The flowers are clustered in cymes. The fruit is a pod and is rarely baccate. There are about 20 genera and more than 250 species in the temperate and subtropical regions of the northern hemisphere, primarily in North America and East Asia. In the USSR there are seven species, representatives of the Hydrangea, Deutzia, and Philadelphus genera.
Many Hydrangeaceae, once wild, often are grown in gardens and parks as ornamental and melliferous plants. The attribution of Hydrangeaceae to the Saxifragaceae family has become obsolete. Hydrangeaceae should be grouped with the Escalloniaceae. The genus Philadelphus and genera closely related to it are sometimes assigned to the special family Philadelphaceae.