Poa pratensis L. syn. Kentucky bluegrass is a strongly rhizomatous, mat-forming, perennial grass. Plants can range from 10 cm to 1 m in height.
Culms are slender and wiry, slightly flattened, and erect to decumbent at the base.
Sheaths are rounded to somewhat keeled, partially closed, and glabrous. All panicle branches are flexuous, and the lower branches occur in a whorl. Cobweb-like hairs occur at the base of the lemmas. Over 100 Kentucky bluegrass cultivars have been developed, resulting in a highly variable species. Canada bluegrass, a similar species found in the park, is distinguishable from Kentucky bluegrass vegetatively by its obviously flattened culm, compressed keel leaf sheaths, and more blue-green appearance.