Agalinis purpurea var. purpurea
Stems 4–120 cm; branches ascending, spreading, or arching. Flowers: calyx tube 3–5 mm; corolla 18–36 mm, lobes spreading to reflexed, (4–)5–11 mm; distal anthers exserted, perpendicular to filaments, pollen sacs 2–4.5 mm; style strongly exserted.
Phenology: Flowering Aug–Oct.
Habitat: Moist sandy soils at margins of ponds, lakes, streams, bogs, freshwater and brackish marshes, ditches, pine barrens, meadows, prairies, coastal swales, dry soils, margins of pine plantations, inundated marl prairies.
Elevation: 0–1100 m.
Ont., Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Tex., Va., W.Va., Wis.
Reports of var. purpurea from Maine have not been verified by the authors.
Variety purpurea is most easily confused with Agalinis harperi but differs from A. harperi by characters used in the key and by having leaves usually as long as, or longer than, the internodes they subtend. Plants of A. harperi have leaves shorter than the elongated internodes. The internodes immediately proximal to the racemes are especially elongated in A. harperi, imparting a much more open appearance than the often bushy and leafy var. purpurea. The narrowly linear-leaved plants of var. purpurea found in brackish marshes and pine barrens appear more leafy than A. harperi because of many axillary fascicles and/or axillary branchlets. The calyx lobes of var. purpurea are variable in shape and length but are not keeled like those of A. harperi.
Plants of var. purpurea usually are easily distinguished from Agalinis fasciculata by their glabrate stems and few to no axillary fascicles versus the often harshly, and more uniformly, scabrous stems and abundant axillary fascicles of A. fasciculata. Variety purpurea has spreading to broadly arching branches; branches of A. fasciculata are ascending from a clearly defined elongated main stem and the terminal racemes arch downward as fruits mature. Some plants of var. purpurea in Arkansas, Louisiana, and Texas are more pubescent than usual and can be confused with A. fasciculata. The larger, recurved trichomes are concentrated along the angles of the main stem and largest branches on A. purpurea. On A. fasciculata the larger trichomes occur on both the angles and faces of the main stem and largest branches. Both taxa may have scabrous branches, especially distally. It is best to evaluate indument on the mid region of the main stem and largest branches when comparing A. fasciculata and A. purpurea.