There are so many Kentucky bluegrass cultivars available that it is difficult to decide which one(s) to plant – especially when it comes to the question of heat and drought tolerance. As a species, Kentucky bluegrass is remarkably heat and drought tolerant as demonstrated by the survivability of bluegrass lawns during the recent drought years.
The most desirable bluegrass for casual use lawns is one that remains green longer between irrigations or rains. Research in Colorado and around the U.S. has demonstrated that certain bluegrass cultivars remain green longer than others during short-term drought and/or watering restrictions. Some of the most drought resistant bluegrass cultivars include: America, Apollo, Baroness, Brilliant, Impact, Mallard, Midnight, Midnight II, Moonlight, Rugby II, Showcase, Total Eclipse, and Unique. Bluegrass cultivars differ little in actual water use rate. It appears that enhanced drought resistance comes from the ability to form somewhat deeper roots than the other bluegrasses.
Limited research (along with many anecdotal field observations) suggests that the Texas bluegrass x Kentucky bluegrass hybrids (Reveille, Longhorn, Thermal Blue, Solar Green, Dura Blue, Bandera) have better than average drought resistance and excellent heat tolerance. These Texas hybrids form extensive root systems and produce large, aggressive rhizomes, making them well-suited for athletic field use.
Mowing any bluegrass turf at 2-3 inches, fertilizing adequately (but not excessively), irrigating deeply but less frequently, and cultivating to relieve soil compaction will increase water use efficiency and turf health.