Mapping here is provisional pending closer inspection of colls. This taxon has been recently described as a segregate of patula, concentrated on clifftops or nearby glades in the Interior Low Plateaus of Ky., plus in disjunct populations as far as the Ridge-and-Valley of Va. to Ga. and the Ozarks of Mo. (M. Brock in Weakley et al. 2023). There are also a few records from Tenn. and Ark. (M. Brock, pers. comm.). S. diffusa is reportedt to differ from typical patula as follows: sepals averaging 3.5-5.2 mm long (versus 4-5.5 mm), with 3 nerves or occasionally 5 (versus 5), widely spaced and not strongly ribbed (versus usually closely spaced and strongly ribbed); inflorescences divaricately-branching at maturity, forming a diffuse tangled mound in robust specimens (versus ascending to spreading); seeds 0.8-0.9 mm wide (versis 0.5-0.75 mm); flowering mostly in May and June (versus April and May). Plants of diffusa has sometimes been referred to S. muscorum (= S. patula var. robusta); see notes under that name. R.K. Raebeler et al. (in FNA 5) indicated that occasional plants of patula "from Ga., Ky. and Va. have glabrous sepals with only three strong veins, resembling those of muscorum; in other features, including the seeds, they are clearly referable to patula. The status of the plants with three-veined sepals remains ambiguous..." These plants can now be called diffusa. However, deeper investigation of diffusa is still needed to clarify diagnostic characters; leaf sizes (perhaps averaging greater in diffusa) and stem thickness (perhaps averaging less) may also be useful in some cases. And there may be intermediate plants. .