Common Gerardia (Slender Gerardia; Slender False Foxglove)
A much-branched, bushy annual, with wiry branches, the main stem with narrow ridges. Flowers single on pedicels arising from leaf axils, light magenta to rose-purple (sometimes white), funnel-shaped with a short tube, 5 distinct lobes having finely fringed margins, and darker purple spots in the throat. The upper lip arches over the 4 hairy stamens. Blooms August-October. Leaves opposite, linear, to 3 inches long and 1/8 inch wide; upper leaves have smaller leaflets growing from axils. Fruit rounded capsules containing many seeds.
Similar species: Eight other species of Agalinis occur in Missouri. Of these, rough-stemmed gerardia (A. gattingeri) is fairy widespread in all but the northwest and extreme southeast parts of Missouri. It grows in acidic soils in dry, open woods and glade borders. Its foliage is yellowish-green, its leaves only about 1 inch long and the flowers pink.