Author: Ward Upham, Kansas State University
Though there are only five regions shown on some turf optimum adaptation maps, there is also an overlapping zone, known as the transition zone, that covers a significant portion of the United States, as seen in the image above. This transition zone includes portions of four of the five turfgrass regions and extends through the central portion of the country from the Atlantic Coast to eastern New Mexico. The transition zone is the most difficult area to grow grass. Warm-season species can be damaged by winter weather, and cool-season species struggle with hot summers. Therefore, choosing a grass species for the transition zone often means choosing the species that is best adapted; not well adapted. This can mean choosing a species that is not necessarily suggested for your region. For example, even though the Cool/Humid region does not recommend any warm-season species, they can and often are grown in the more southern locations of this region. Also, cool-season species that are recommended may not do as well as expected along those same southern extremities.