Clusters of white flowers are blooming in fields and open forests in western Pennsylvania.

Yarrow (Achillea millefolium) is a perennial in the Aster family, native to the northern hemisphere.  The genus name, Achillea, refers to the Greek hero who reportedly used yarrow to treat his soldiers’ wounds.  The species name, millefolium, means “a thousand leaves.” Look closely at the tiny feather-like leaves and you’ll see they’re arranged in a spiral on the stem.

Yarrow’s flowers deserve a closer look, too.  The central disk is a cluster of tiny flowers and the petals (rays) are individual flowers with nectar openings where the ray connects to the flower head.

In North America we have both native and introduced species and they hybridize so it’s hard to tell who’s who.

Watch for yarrow blooming this month and into June.

(photo by Kate St. John)