This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Shrubs, with opposite leaves, and yellow axillary and terminal cymose or solitary flowers. Calyx-tube slender, elongated, narrowed below, the limb with 5 linear persistent lobes. Corolla narrowly funnelform, the tube slightly gibbous at the base, the limb nearly regular, 5-lobed. Stamens 5, inserted on the corolla; anthers linear. Ovary 2-celled; ovules numerous in each cavity; style filiform; stigma capitate. Fruit a linear-oblong capsule, narrowed or beaked at the summit, septicidally 2-valved, many-seeded. Seed coat minutely reticulated; endosperm fleshy; embryo minute. [Named for Dr. Dierville, who brought the plant to Tournefort]
Three species, the following typical one, the others in the mountains of the Southern States. The Japanese and Chinese Weigelas, often referred to this genus, are here regarded as distinct.
A shrub, 2°-4° high, glabrous or nearly so throughout, with terete branches. Leaves short-petioled, ovate or oval, acuminate at the apex, usually rounded at the base, 2's' long, irregularly crenulate and often slightly ciliate on the margins; peduncles terminal, or in the upper axils, slender, 1-5-flowered; flowers about 9" long; corolla more or less pubescent both without and within, regular or slightly irregular, 3 of its lobes somewhat united; capsule glabrous, linear-oblong, slender, beaked, crowned with the persistent calyx-lobes.
In dry or rocky woodlands, Newfoundland to Manitoba, North Carolina, Michigan and Wisconsin. Gravel-weed. Life-of-man. May-June.