The third primary cultural practices in turfgrass management is irrigation. Lack of irrigation (e.g., prolonged summer drought) causes turf to go dormant and survive via crowns, rhizomes, and stolons; turf density decreases, which allows weeds to compete freely once fall rains come or irrigation begins. Once weeds are established, they often thrive under this drought cycle because many are exceptionally deep rooted. Lawns allowed to go dormant every summer require more intensive efforts to control weeds chemically than lawns that are irrigated enough to ensure optimum turf density.
Irrigation should be applied at a 0.25" depth per application 3 to 6 times per week totally 0.75" to 1.5" per week depending on the turfgrass species and environmental conditions. Kentucky bluegrass, perennial ryegrass and fine fescue will require more irrigation to maintain high quality turfgrass, while tall fescue and bentgrass will require less irrigation. Weeds that are an indication of too little irrigation include false dandelion and summer annuals like crabgrass.