Although root development is critical in the establishment of turfgrass sod, there appears to be no information on the response of root development during sod establishment to the frequency and amount of irrigation. Two alternate hypotheses for the root development response are that 1) frequent and high amounts of irrigation are needed to support sod growth and root development; and 2) deficit irrigation encourages more rapid and deeper rooting. The objective of this study was to observe root development of four warm-season turfgrasses subjected to various frequencies and amounts of irrigation. Root extension of the grasses was observed directly in soil contained in 90-cm tall, clear acrylic columns. No difference in root development was observed for any of the grasses among irrigation frequency treatments of daily, twice weekly, and once weekly. There were differences in response to the amount of irrigation. Zoysiagrass root development was maximal at the full amount of irrigation (35 mm per week). On the other hand, St. Augustinegrass, bermudagrass, and bahiagrass required deficit irrigation of only 13 mm water per week to achieve full root development. The results of this study showed that each of the two hypotheses were appropriate depending on the specific species.