Zoysia grass is a dense, fine-to-medium textured turfgrass known for its heat and drought tolerance, classifying it as a warm-season grass. Unlike cool-season varieties, Zoysia spreads laterally through above-ground runners called stolons and underground stems called rhizomes, creating a thick, carpet-like surface. Converting an existing lawn to Zoysia often involves a gradual process using small plugs, allowing the new Zoysia to establish roots and slowly outcompete the old turf over one to three growing seasons.
Preparing the Existing Turf for Zoysia
The first step is weakening the existing turf so the Zoysia plugs have a competitive advantage, especially against vigorous cool-season grasses like fescue or bluegrass. Planting must occur during Zoysia’s active growth phase, typically from late spring through early summer when soil temperatures are reliably warm. The existing lawn must be mowed down to its lowest setting, ideally one inch or less, a process known as scalping. Following scalping, dethatch the lawn or use a vertical mower to remove excess organic material, ensuring the new Zoysia plugs make direct contact with the mineral soil for faster root establishment. Before planting, conduct a soil test; Zoysia performs best in a pH range of 6.0 to 6.5, and any necessary amendments should be applied and worked into the topsoil.
Planting Methods and Application
The most effective method for gradually converting an existing lawn is planting Zoysia plugs, which are small, rooted sections of sod. Plugs are preferred over seeding because Zoysia seed viability is inconsistent, making establishment slower and less reliable. Spacing determines the rate of establishment; planting plugs 6 inches apart results in coverage in one to two seasons, while 12-inch spacing extends conversion time to two or more years.
Use a specialized plugger tool or bulb planter to ensure the planting holes are the correct size and depth. Each plug must be inserted firmly into the soil so its crown is flush with the ground surface, eliminating air pockets that cause drying and failure. Immediately after planting, apply a starter fertilizer high in phosphorus, such as a 12-12-12 formula, to stimulate vigorous root development and encourage quick anchoring.
Establishing the Zoysia and Outcompeting Old Grass
The period immediately following planting requires a specific watering regimen to prevent transplant shock. For the first two to three weeks, provide frequent, light watering daily to keep the plugs and topsoil consistently moist. Once the plugs show new growth, gradually reduce the frequency, transitioning to deeper, less frequent irrigation, aiming for about one inch of water per week. This change encourages the Zoysia to develop a deep, drought-tolerant root system.
Maintaining a short mowing height of 1 to 2 inches must continue during the establishment phase. This practice deprives the taller, existing grass of sunlight and energy, suppressing its growth while allowing maximum sunlight to reach the Zoysia plugs. Aggressively manage competition from the old turf and any weeds that sprout between the plugs. Selective herbicides are often necessary for larger lawns; products containing Dicamba or 2,4-D are generally safe for Zoysia broadleaf weeds. Pre-emergent herbicides can also prevent new weed seeds from germinating. Avoid applying excessive nitrogen fertilizer too early, as this can inadvertently stimulate the existing grass. Once the plugs actively spread (six to eight weeks after planting), apply a light application of a nitrogen-heavy fertilizer (one pound of actual nitrogen per 1,000 square feet) every four to six weeks during the peak summer growing season to accelerate the Zoysia’s takeover.