Phlox (Polemoniaceae) is a family of flowering plants ranging from leafless annual herbs to small trees and vines. Most species occur in North America, particularly in the western desert and in dry, cold regions. About 300 species are known worldwide. The genus Phlox is the best-known member of the family; 11 species occur in Canada. Wild blue phlox (P. divaricata), found in eastern Canadian open woodlands, blooms in May. In western Canada, P. hoodii (moss phlox) and P. diffusa (spreading phlox) form mats of colour ranging from white to bright mauve and pink in open prairie grassland and in foothill regions of the Rockies, April-June.

Tall, vibrantly coloured summer-flowering phlox, derived from eastern North American P. paniculata, one of the most popular garden perennials in Canada, is often used for island beds or as border plants. Many flower colours are available and most produce a sweet fragrance during the July-September flowering period. Sweet William, a traditional garden plant, developed from P. maculata (native from Québec to Virginia) and is a popular cut flower.