Periwinkle   
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Vinca major, with the common names bigleaf periwinkle, large periwinkle, greater periwinkle and blue periwinkle, is species of flowering plant in the family Apocynaceae, native to the western Mediterranean. Growing to 25 cm (10 in) tall and spreading indefinitely, it is an evergreen perennial, frequently used in cultivation as ground cover. Photo Claire Weiss (9/Feb/2014)
Five petals
Lea Marshes Botany