Mow the lawn at higher levels each time. There is a direct correlation between grass height and root depth; the higher the grass is cut, the deeper the roots grow. Deeper roots help your lawn ensure heat and environmental stress better than before.
Water the grass for longer periods of time, but less frequently. The soil should be moist at least 4 to 6 inches below the lawn's surface to produce taller grass. This will help the soil remain moist long after the lawn's surface has dried. A deep soak watering will also induce the roots to reach deeper into the soil. Lighter and more frequent watering, on the other hand, will induce shallow roots.
Make sure the grass contains good quality soil. The type of soil you have will either encourage or discourage taller grass. Use organic matter, such as compost, to loosen the soil, provide nutrients, increase water retention and provide better air exchange
Fertilize the grass. Use slow-release fertilizers to promote grass root growth, which ultimately will make the grass grow taller. Make sure that the fertilizer is watered into the grass because the high salt content of mineral fertilizers can cause your lawn to burn.