Transition Zone Map
June 10, 2022


By James Weiss

The U.S. can be divided into areas to determine which species perform best in climates that match their growth patterns. Planting species that do well in these zones are both environmentally and economically friendly. Think thriving plants, less outrageous water usage and higher tolerances to drought and disease.

In the cool-season zone, species experience optimum growth at temperatures between 60 and 75°F (15.5 to 24°C) which are typically during the spring or fall months. This zone encompasses the northern half of the U.S. Examples of grasses that are common in the cool-season zone include Fine Fescue, Tall Fescue, Kentucky Bluegrass, and Perennial Ryegrass.

The warm-season zone is considered the most southern area of the U.S. where species actively grow during the warmest months, at temperatures between 80 and 95°F (27 to 35°C). This optimum growth occurs in the spring or summer. Examples of grasses that are common in the warm-season zone include Bahiagrass, Bermudagrass, and Zoysiagrass.

The transition zone is the middle ground where conditions from both the cool-season and warm-season zone are present. This zone experiences winters that are too cold for warm-season species and summers that reach temperatures too hot for cool-season species. It is common for warm-season species, especially grasses, to be grown during the warmest months, then overseeded with cool-season species that will grow best during the spring and fall. Problem solved.

With the goal of keeping things simple, three zones are plenty to choose from. Even though your location may not consistently experience these optimal temperatures, the zone that is the closest match will suffice. Or to make things easier, refer to the graphic to determine which zone your state appears in.

While the cool-season or warm-season zones are most commonly used to categorize grasses, other plants can fit in these temperate categories as well. Crops, forage species, natives, or wildflowers that are more tolerant of colder months fit into the cool-season zone while species that thrive in warmer temperatures are considered part of the warm-season zone.