I've been watching these Guelder Rose~Virburnum opulus flower heards for a while to show you that the flowers are in the centre of the flowers head that is surrounded by flower like bracts.
The common name 'guelder rose' relates to the Dutch province of Gelderland, where a popular cultivar, the snowball tree, supposedly originated.Other common names include water elder, cramp bark, snowball tree and European cranberry bush, though this plant is not closely related to the cranberry.
Viburnum opulus is a deciduous shrub growing to 4?5 m (13?16 ft) tall. The leaves are opposite, three-lobed, 5?10 cm (2?4 in) long and broad, with a rounded base and coarsely serrated margins; they are superficially similar to the leaves of some maples, most easily distinguished by their somewhat wrinkled surface with impressed leaf venation. The leaf buds are green, with valvate bud scales.

The hermaphrodite flowers are white, produced in corymbs 4?11 cm (2?4 in) in diameter at the top of the stems; each corymb comprises a ring of outer sterile flowers 1.5?2 cm in diameter with conspicuous petals, surrounding a center of small (5 mm), fertile flowers; the flowers are produced in early summer, and pollinated by insects. The fruit is a globose bright red drupe 7?10 mm diameter, containing a single seed. The seeds are dispersed by birds.
Susan