Cool & Warm Season Grasses

map showing zones for warm and cool grassesTurfgrasses perform more effectively within temperatures that most closely match their growth patterns.

Few regions are consistently within the optimum temperature range. Many areas do provide those temperatures for varying periods of the year.

Turfgrasses are divided into two temperature categories: cool season and warm season.

Cool-season turfgrasses are those species with optimum growth at temperatures between 60 and 75°F (15.5 to 24°C). Cool season grass species include creeping bentgrass, fine fescue, tall fescue, Kentucky bluegrass, annual ryegrass and perennial ryegrass.

Warm-season turfgrass are those species with optimum growth at temperatures between 80 and 95°F (27 to 35°C). Warm season grass species include Bahiagrass, bermudagrass, carpetgrass, St. Augustine and zoysiagrass.

To make it easier to determine the appropriate species selection, geographic areas are designated as zones according to temperature range. Warm-season and cool-season are two of these zones as shown on the US map.

Within geographic zones, other climatic conditions occur which further impact turfgrass growth. Two primary factors are conditions which are predominantly humid or predominantly arid.

Some geographic areas are designated by combining those factors with the temperature range. For the US, that combination yields four zones: cool/humid, cool/arid, warm/humid and warm/arid.

A fifth geographic area, designated as the transition zone, occurs where conditions from all four of the other zones are present. This is the most difficult zone in which to grow turfgrasses. It is typically too cold in the winter for the warm season grasses and too hot in the summer for the cool season grasses.

Some people compensate for this dilemma by growing warm season grasses during the time of the year when temperatures favor them. They then overseed the warm-season grasses with species of cool-season grasses that will grow when temperatures favor them. The transition zone is shown on the US map.

Plant breeders have developed multiple varieties within each of the species. These display distinctive characteristics in areas of: density, color, leaf texture, shade tolerance, wear tolerance, heat tolerance, drought tolerance, disease resistance, fertility and maintenance requirements, and carbon footprint.

To find the best match in cool-season grasses view this chart.

To find the best match in warm-season grasses view this chart.

This information provided by The Lawn Institute – www.TheLawnInstitute.org

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