Flower:

Flattish, branching clusters of a few to several flowers at the ends of branching stems in the upper plant. Individual flowers are 1/3 to 2/3 inch across, have 7 to 15 white ray flowers (petals), notched at the tips, and pale gray-brown center disc flowers.

Double flowers with 20+ rays are common. The bracts surrounding the base of the flower are in 3 layers, green with brown edging, covered in matted hairs.

Leaves and stems:

Leaves are alternate, lance-linear, 1 to 4 inches long, less than ¼ inch wide, hairless except along the midrib on the underside, finely toothed around the edges, and stalkless. Stems are mostly erect, usually branched, hairy on the upper stems and usually smooth below. Plants can form colonies from spreading rhizomes.

Fruit:

Flower heads become seed heads about ¼ inch in diameter. Fruit is a dry seed about 2mm long.

Notes:

An infrequent weed in Minnesota, Sneezewort has been cultivated globally and occasionally escapes cultivation. The flowers resemble Common Yarrow (Achillea millefolium), which is more densely flowered, the flowers have only 4 to 6 rays, and leaves are finely divided and feathery. The double-flowered form of Sneezewort, known as “the pearl”, is common in the garden trade and both forms can persist in the wild.