Stems branched, 15–70 cm; branches laxly and widely spreading, proximal arching upward, subterete proximally, quadrangular, with siliceous ridges and wings on angles distally, glabrous, sometimes scabridulous. Leaves spreading to spreading-ascending; blade linear, 8–30 x 0.5–2.3(–3) mm, not fleshy, margins entire, siliceous, adaxial surface finely scabrous; axillary fascicles absent. Inflorescences racemiform, with lateral branches bearing solitary flowers, flowers 1 per node; bracts both shorter and longer than, or shorter than, pedicels. Pedicels spreading to spreading-ascending or arching, 3–14 mm, glabrous. Flowers: calyx campanulate, tube 3–5.5 mm, glabrous, lobes lanceolate, 1.3–2.5 mm; corolla pale pink (sometimes nearly translucent), with 2 yellow or pale lines and pale purple spots in abaxial throat, 8–12 mm, throat pilose externally and villous within across bases and sinus of adaxial lobes, lobes: abaxial spreading, adaxial reflexed-spreading, 3–5 mm, glabrous externally; proximal anthers parallel to filaments, distal perpendicular or oblique to filaments, pollen sacs 0.8–1.5 mm; style exserted, 3–5 mm. Capsules obovoid, 4–6(–7) mm. Seeds tan to pale brown, 0.8–1 mm.
Phenology: Flowering late Aug–Oct.
Habitat: Mesic to wet areas of prairies, moist to wet savannas, moist roadsides, mesic to wet edges of recently clear-cut forests, dry or wet roadsides.
Elevation: 0–100 m.
Ala., Ark., La., Miss., Mo., Okla., Tex.
Agalinis viridis is tolerant of mowing and grazing; plants severed at mid stem will flower vigorously from the proximal nodes