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..
Herbs, with opposite leaves, no prickles, and blue pink or white flowers in peduncled involucrate heads. Bracts of the involucre herbaceous, separate, or slightly united at the base. Scales of the pubescent receptacle none. Involucels compressed, the margins often minutely 4-toothed. Calyx-limb 5-10-awned. Limb of the corolla 4-5-cleft, oblique or 2-lipped. Stamens 4 (rarely 2). Stigma oblique or lateral. Achene more or less adnate to the involucel, crowned with the persistent calyx. [Latin, scale, from its repute as a remedy for scaly eruptions ]
About 75 species, natives of the Old World. Type species: Scabiosa arvensis L.
Scabiosa arvensis L. Sp. Pl. 99. 1753. Knautia arvensis T. Coult. Dips. 29. 1823.
Perennial, pubescent, simple or little branched. 1°-3° high. Basal and lower leaves petioled, lan-seolate, acute or acuminate, entire, lobed, or pin-natifid, 3'-8' long; upper leaves sessile, often deeply pinnatifid; heads long-peduncled, depressed-globose, 1'-11/2' broad; flowers lilac purple, about 6" long; receptacle depressed-hemispheric, not scaly, covered with hairs between the flowers; achene angled, crowned with the 8 or 10 linear-subulate calyx-teeth.
In cultivated fields and waste places, Quebec to Massachusetts, Vermont, New York and Pennsylvania. Adventive from Europe. Other English names are blue buttons, blue caps, gypsy- or egyptian-rose, pincushion. June-Sept.