Zoysia grass is a warm-season turf variety highly favored across Georgia due to its dense growth habit and impressive tolerance for the region’s hot, humid summers. Achieving a lush, carpet-like lawn requires a strategic approach to nutrient management. For Zoysia to maintain its vigor, density, and color throughout the growing season, a timely fertilization regimen is necessary. The success of this regimen depends less on the calendar date and more on understanding the grass’s biological needs as dictated by soil temperature.
Understanding Zoysia’s Active Growing Season in Georgia
As a warm-season grass, Zoysia’s emergence from winter dormancy depends entirely on soil temperature, not air temperature. The critical period for active growth is “green-up,” which initiates when the soil temperature at a four-inch depth consistently reaches 65°F. This temperature threshold signals that the grass roots are actively taking up nutrients and can process fertilizer effectively. Applying nitrogen fertilizer before this temperature is reached is inefficient and potentially harmful. Early application risks nutrients leaching away or encourages tender new growth, making the grass susceptible to late spring frosts or disease.
The Annual Fertilization Schedule
First Application
The first fertilizer application should coincide precisely with the period immediately following full spring green-up, generally in late May or early June. This initial feeding supports the grass as it begins its most vigorous period of growth. Wait until the lawn is fully green, indicating the root system is prepared to utilize the nitrogen.
Mid-Summer Feeding
A second application is recommended during the peak of summer, typically between mid-July and early August. This mid-summer feeding sustains the lawn through the highest temperatures and sun exposure. The goal is to provide a steady supply of nutrients every four to six weeks during the active growth period, if the lawn requires additional nitrogen.
Final Application
The final nutrient application should occur in late summer or very early fall, with a strict deadline of no later than September 1st. This application must focus primarily on potassium, with little to no nitrogen included. Applying nitrogen past this deadline is detrimental, as it encourages soft, leafy growth that does not harden off before the first frost, making the grass susceptible to winter injury and fungal diseases.
Selecting the Appropriate Fertilizer Blend
For established Zoysia lawns, a fertilizer blend providing a balanced ratio of nitrogen (N), phosphorus (P), and potassium (K) is recommended, often following a 4-1-2 ratio. Common N-P-K formulations include 16-4-8 or 12-4-8. The total amount of actual nitrogen applied annually should range from 2 to 4 pounds per 1,000 square feet, with the higher end reserved for lawns on sandy soils. A significant portion of the nitrogen should be in a slow-release form. Slow-release nitrogen is metabolized gradually, preventing a sudden surge of growth that can lead to excessive thatch buildup and increase the risk of fungal disease. This helps the turf maintain a consistent appearance and better withstand heat stress. Before selecting any fertilizer, conduct a soil test, which provides a detailed analysis of existing nutrient levels and pH. A soil test is the only way to accurately determine if the lawn has sufficient phosphorus and potassium, allowing for precise selection and avoiding over-applying unnecessary nutrients.
Essential Supporting Care Practices
Mowing and Watering
Effective fertilization must be paired with disciplined maintenance practices to ensure nutrients are used efficiently. Mowing Zoysia grass at the correct height encourages a dense turf canopy that suppresses weeds and improves health. The recommended mowing height is between 1 and 2 inches, and the lawn should be mowed frequently so that no more than one-third of the grass blade is removed. Zoysia requires deep, infrequent watering, aiming for three-quarters to one inch of water per week, including rainfall, which encourages a resilient, deep root system.
Post-Application Care
Immediately after applying a dry granular fertilizer, the lawn must be watered lightly to wash the granules off the grass blades and into the soil. This prevents the fertilizer from causing chemical burns on the leaf tissue, which appear as scorch marks. Watering in the early morning is recommended to ensure the grass blades dry quickly, helping reduce the risk of fungal diseases.