Plugging is exactly what it sounds like — plugging small squares or circles of sod into the soil at regular intervals. Square plugs are cut from sod with a shovel or knife; round plugs are cut with a special steel plugger that works like a bulb planter. You may buy sod and cut the plugs yourself, but it is easier to order precut plugs by mail. The 2- to 4-inch plugs come in trays of 18, which will plant about 50 square feet. They have a root system that will quickly establish itself. Plugging is generally used only for warm-season grasses, such as centipedegrass, St. Augustinegrass, and zoysiagrass.
When to plug
Plant plugs just before spring weather begins. It is critical to prepare the soil correctly before the plugs arrive, for they need to be planted as quickly as possible. Although they have soil and roots of their own, they can dry out rapidly. If you anticipate a delay in planting, keep them moist by covering them with plastic away from direct sunlight.
How to plant plugs
Before the plugs arrive, use a steel plugger (or a trowel or small shovel) to make holes of the proper size; usually 1 inch wider and deeper than the plugs themselves. Space the holes 6 to 12 inches apart, depending on the size of the plugs and type of grass (bermudagrass, centipedegrass, St. Augustinegrass, or zoysiagrass). Of the warm-season grasses used for plugging, bahiagrass and bermudagrass spread the fastest, and centipedegrass and zoysiagrass spread the slowest. Gauge planting distances accordingly. To help the lawn take hold evenly, offset the rows of plugs in a checkerboard pattern. Soil taken from planting holes should be spread evenly over the ground between the holes.
When the plugs arrive, lightly moisten the soil and then place the plugs into the holes. Firm the soil around them so that the crowns of the plants (the points where leaf blades converge at the soil line) are level with the ground. Then roll and water the plugs. Although plugs do not dry out as fast as sprigs, keeping the soil around them moist is still important. Water them daily for the first two weeks so that they do not dry out. Then, depending on the weather, you can water every other day for a month or until the plugs are well established (their roots firmly knitted with the soil below). To check for this, lightly pull on a plug — if it resists, you know that the roots have taken hold.
When the plugs have established themselves, mowing should begin. Frequent mowing will stimulate the growth of stolons along the soil, making the grass spread more rapidly. The plugs can be fertilized every 6 to 8 weeks until the entire planted area has filled in. The closer together the plugs were planted, the sooner the lawn will cover the area.
After plugging, watering and rain may cause the soil to wash out between plugs, yielding an uneven and bumpy lawn. Once the roots have taken firm hold but before the plants begin to spread, you will probably need to add extra soil between the plugs to level the lawn.
Plugging is the slowest method of establishing a lawn. (Unlike sprigs, which start out stretched prone across the soil, the grass in plugs must take extra time to extend itself by sending out new rhizomes and stolons.) Zoysiagrass, the major species propagated by plugging, may take two years to fill in a lawn.