Cool Seasons Grasses and Grass Growth



Cool Season Turfgrasses

In most parts of the country, cool season turfgrasses have a seasonal pattern. They emerge from dormancy and grow rapidly in the spring. Cool season grasses can tolerate the summer conditions; however, they may turn brown and go dormant in high heat and drought conditions.

As the weather cools in the fall, and rains return, growth resumes. This growth continues until the soil freezes. Although in some regions of the country, like the Pacific Northwest, cool season grass species are active all year long.

Cool season grasses are much more tolerant of shade than are warm season grasse and grow best with 8 or more hours of full sun per day. Even shade-tolerant species of cool season grasses require at least 50% full sun.


Optimal cool season turfgrass leaf and shoot growth is when daytime air temperatures are between 60°F and 75°F and nighttime air temperatures are in the mid 50s. Leaf growth is minimal when air and soil temperatures are below 50°F. As air temperatures rise above 80°F, leaf growth slows down dramatically.

Soil temperatures regulate root growth. Maximum root growth for cool season turf occurs when soil temperatures are between 50°F and 65°F. Root growth occurs as long as the soil is not frozen (but temperatures are still low) and continues until soil temperatures rise above 45°F. When soil temperatures reach 75°F in the top inch of soil, root growth is greatly reduced. Roots close to the surface can dieback when soil temperatures reach 90°F.

Cool Season Fertilization and Carbohydrates

Excessive spring fertilization can reduce carbohydrate reserves and root development by stimulating rapid shoot growth. Shoot growth takes priority over roots for carbohydrate utilization.

Late fall fertilization is applied when shoot growth slows, but root growth is still active. Fall nitrogen applications greatly enhance the production of carbohydrates. These carbohydrates are stored for use the following growing season and enhance early spring green-up.

Scotts LawnService is the trusted industry leader for professional quality lawn care. Our exclusive lawn care products include premium grass seed and professional-grade turf and lawn fertilizers; our lawn service teams are comprised of highly trained, industry-certified professionals. Contact a representative today for help choosing the right cool season grass fertilizer for your yard and to learn how you can enjoy a lush, thicker lawn that only Scotts LawnService can deliver.