Grass drought tolerance and avoidance

I have heard that buffalograss is more drought tolerant than fescue, but then I have also been told that fescue has a deep root system to help it survive drought. Which is right?

First let's define drought. If drought is a couple of weeks without water, then the second answer is correct. If drought is typical New Mexico conditions with limited water for prolonged periods, then the first answer is correct.

Plants survive periods without water by using a couple of strategies. Fescue "avoids" drought by using its deep root system to find water when the surface is dry. However, if the soil dries to a depth greater than the roots, it has a problem. To continue to avoid drought, the leaves roll reducing water loss, but this avoidance strategy is only a last resort and the grass must be irrigated soon after leaf-rolling begins.

Buffalograss also uses avoidance strategies, but it also uses a "tolerance" strategy. Buffalograss and some other drought-tolerant warm-season grasses tolerate dry periods by increasing the osmotic potential within their cells to reduce wilting and help them survive drought.

In a recent study from Kansas State University published in the "Journal of the American Society for Horticultural Science", buffalograss, bermudagrass, and zoysia were shown to be more tolerant of drought and to recover more rapidly than tall fescue. Grasses were allowed to dry until they were wilted and brown then rewatered. Two weeks after watering, buffalograss exhibited 50 percent green coverage while tall fescue showed only 4 percent green. Zoysia grass was 22 percent green and bermudagrass was 14 percent green.

Based on this information, buffalograss is more likely to tolerate drying and rapidly recover when water is again available. However, another factor reported was that well- watered tall fescue grew more rapidly. This means that well- watered tall fescue will require more mowing but will also tolerate wear from athletic and other traffic better than buffalograss. If the grass must remain green into the fall and green early in the spring, tall fescue again has the advantage.

It is important to consider all factors when choosing a turfgrass. Drought tolerance is one, so is the purpose for which it is used and the season in which the use is important. It is also important to consider the part of New Mexico in which the grass is to be grown. Tall fescue does better in cooler parts of the state, requires more water, mowing, and is slower to recover from drought. Buffalograss grows in all parts of New Mexico, does not require as much water and mowing, recovers more rapidly from drought, but it does not grow as rapidly to recover from traffic. It is also dormant longer during the cool season.

In warmer parts of New Mexico, bermudagrass is often the preferred grass. In the cool season it is often overseeded with perennial rye to provide a longer season of green grass.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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