Tall fescue is a cool-season perennial grass, meaning its care calendar is dictated by moderate temperatures. Unlike warm-season grasses, fescue actively grows primarily in the spring and fall. The extreme heat and humidity of an Oklahoma summer force the grass into a period of stress. Therefore, precise fertilization timing is the most important factor for its survival, maximizing growth during favorable conditions and preparing the plant for harsh summer dormancy.
Understanding Fescue Needs in Oklahoma’s Climate
The physiology of cool-season grasses dictates a specific fertilization strategy in Oklahoma. Fescue’s most vigorous root growth occurs when soil temperatures are cool, typically between 50 and 65 degrees Fahrenheit. This allows the plant to develop a deep, robust root system capable of accessing water and nutrients before summer stress arrives.
The plant’s top growth is most active in the spring when air temperatures are mild. During the summer months, generally June through August, fescue enters semi-dormancy, slowing growth to conserve energy. Fertilizing heavily during this period of high heat and moisture stress is counterproductive. It encourages excessive leaf growth that the compromised root system cannot sustain. Therefore, maintenance must build plant strength in the cool seasons, preparing it for the summer slowdown.
The Essential Fall Fertilization Schedule
Fall is the most important period for fertilizing tall fescue in Oklahoma, as applications made now support the plant through the following year. This season allows for three distinct feeding windows, each with a specific purpose. The first application should occur in early September, targeting the grass’s emergence from summer dormancy. This feeding provides readily available nitrogen to stimulate recovery and begin thickening the turf canopy.
The second feeding window is in mid-to-late October or early November. This application coincides with the fescue’s peak root development period. A fertilizer with a higher nitrogen content, such as a 4-1-2 ratio (e.g., 20-5-10 blend), is recommended to drive deep root growth and carbohydrate storage. Applying approximately one pound of actual nitrogen per 1,000 square feet strengthens the below-ground structure for winter survival.
The final fall application is the “winterizer,” applied between late November and mid-December, just before the ground freezes. This feeding utilizes cooler temperatures to maximize nutrient storage within the plant crown and roots. The nitrogen applied now will not stimulate much top growth. However, it will be immediately available for an early green-up the following spring. This three-step fall program ensures the fescue has the energy reserves to withstand winter and flourish when the growing season returns.
Strategic Spring Fertilization and Caution
Spring fertilization is a secondary concern for tall fescue and requires caution in Oklahoma’s climate. A single, light application should be made in late February or early March to provide a boost for initial green-up. This early feeding helps the grass quickly emerge from winter rest and utilize the stored energy from the fall.
The primary goal of spring care is to avoid promoting excessive top growth vulnerable to summer heat. Applying high amounts of nitrogen beyond early spring forces the plant to expend energy on foliage instead of maintaining root depth. This creates a weak, shallow-rooted plant. It will quickly suffer from heat and drought stress when temperatures rise in May and June.
Therefore, any spring application should be very light, ideally using only 0.2 to 0.5 pounds of actual nitrogen per 1,000 square feet. It is necessary to avoid any further nitrogen applications past early spring, such as in late April or May. The risk of the resulting flush of growth burning out in Oklahoma’s intense summer heat far outweighs the temporary benefit of a darker green color.