This annual is centered in the Ozark region but extends through much of the Mississippi watershed (K), mostly on calcareous, cherty or sandy soils that are xeric to xerohydric. It has often been confused with other species and overlooked in Ky., where it appears largely restricted to remnants of former grassland (or barrens") in western regions and in scattered areas along the western margins of the Appalachian Plateaus. Some records here from western regions on relatively damp sites have been tentatively included here, based on misidentified decemloba or skinneriana. Section Erectae, including gattingeri, skinneriana and decemloba, may be a largely natural group with 2n = 26 (versus 28 in other eastern Agalinis). But recent molecular evidence indicates that gattingeri does not fit so clearly into Erectae (Pettengill & Neel 2008). In published keys it is sometimes hard to use the generally distinctive "yellowish-green" color of Erectae, "not tending to blacken in drying" (versus blackening in Tenuifoliae) and with the calyx-tube remaining more "evidently reticulate-veinose" than Tenuifoliae (Pennell 1935). A. gattingeri often has a slightly dark color, but not uniformly developed. Another useful character of Erectae in Tenn. and Ky. (D. Estes, pers. comm.) is that pedicels are longer than bracteal leaves (versus shorter in almost all other Agalinis). But compared to other Erectae, gattingeri tends to have longer leaves, up to 2-3 cm, which curl when dried (versus up to 1-2.5 cm and usually not curling), resembling Tenuifoliae. Leaves remain relatively long even in the inflorescences, which tend to have relatively long branches with flowers distally concentrated (versus more densely flowered racemose branches in other species). Its flowers tend to have longer stigmas (2-3 mm versus 1-2 mm).