Complex sentence: The flowers are produced in spring and summer in button-like clusters, each flower small, white, with four petals 4-8 mm long and 2-3 mm broad, arranged in a cross shape.
Split into simpler sentences: The flowers are produced in spring and summer in button-like clusters. Each small flower has four white petals 4-8 mm long and 2-3 mm broad, arranged in a cross shape.