Another common name for Philadelphia daisy (Erigeron philadelphicus) is Philadelphia fleabane. Historically, bundles of a European cousin were dried and hung in houses in the belief that the plant would get rid of fleas. The name fleabane eventually was applied colloquially to several members of the species.
A tea of Philadelphia daisy was used by Native Americans for chronic diarrhea, gout and epilepsy. Headache and sores were treated with a whole-plant poultice. Care was necessary when using Philadelphia daisy medicinally because it can cause miscarriage.
A native biennial or short-lived perennial, Philadelphia daisy grows throughout most of North America, but is not found in Arizona or Utah. It prefers moist locations and is partial to full sun. Philadelphia daisies grow from .75 feet to 2.5 feet in height.
Growing from a taproot, Philadelphia daisy begins as a low rosette of leaves that begin to dry and disappear once the plant bolts in the spring. The stem is unbranched except near the inflorescence. Going up the stem the alternate leaves become smaller and more spaced. The lower leaves are sparingly toothed while the upper leaves are entire (not toothed). The leaves slightly clasp the stem. Both the stem and leaves are lightly hairy.
Atop the Philadelphia daisy stem is a panicle (a branched inflorescence where the flowers mature from the bottom upward). Panicles also develop from the axils of upper leaves. The daisy-like flowerhead consists of 100 to 300 white to light pink or light violet, thread-like rays surrounding a dense head of yellow disk flowers. Bracts (involucres) surround the flowerhead. The flowers close at night and open again in the morning.
I photographed these Philadelphia daisies in the meadow upstream from the Lower Campground at Ash Creek (Lassen County CA).