A floristic inventory within southeastern Colorado and southwestern Kansas was completed during the field seasons of 2007 and 2008. This area included the Cimarron National Grassland and Comanche National Grassland as well as adjacent private land. The study area is 1,926 square miles, spread over Baca, Otero, and Las Animas counties in Colorado and Morton County in Kansas. Elevation ranges from 3,200 to 6,444 feet. This survey is based on 9,281 collections representing 633 unique taxa. Exotic taxa comprised 16.5% of the flora (107 taxa) of which 16 are listed as noxious weeds. A total of 24 rare taxa were documented. In addition, two state records were added to the flora of Colorado, Astrolepis integerrima (Hook.) D.M. Benham & Windham and Digitaria pubiflora (Vasey) Wipff. Cyperus retroflexus Buckley, collected on the Cimarron National Grasslands, is an addition to the flora of Kansas. This thesis discusses methodology, boundaries of study area, climate, geology, soils, vegetation types, and a floristic comparison using Sørenson's coefficient of similarity. The annotated checklist of vascular plant taxa collected during the study comprises the primary contribution.

This checklist has 785 species and 801 taxa (for taxa, the varieties and subspecies are included in the count) in 90 plant families. The most common plant families are the grasses (Poaceae) and the sunflower family (Asteraceae). Of this total, 513 taxa are definitely known to occur on the Comanche National Grassland. The remaining 288 taxa occur in nearby areas of southeastern Colorado and may be discovered on the Comanche National Grassland.