Kentucky Bluegrass

How long will Kentucky bluegrass or tall fescue survive when dormant?
July 21, 2012

The most common question we are answering now is about how long lawns can go without watering and still survive. Either because of drought or perhaps to conserve water, cool-season grasses can be allowed to go dormant in extended droughts. Once Kentucky bluegrass (KBG) goes fully dormant from drought, the rule of thumb is to water ¼” of water about every four weeks to keep the crowns hydrated and to help insure survival. Upon return of cooler temperatures and increased rain/irrigation, KBG should regreen with only minimal thinning assuming no traffic during dormancy. Traffic during dormancy may damage crowns and increase thinning upon recovery. Excess heat that we are experiencing should likely not significantly affect KBG during dormancy.

Turf-type tall fescue (TTF) will go dormant much later than KBG under similar conditions. This is because TTF is deeper-rooted than KBG and accesses water deeper in the profile. Tall fescue actually uses significantly more water than KBG. Tall fescue has poorer drought survival than KBG and thus we usually recommend to irrigate often enough to prevent tall fescue from going into complete dormancy. Given the extremely dry conditions, it’s likely impossible to prevent dormancy in TTF. Therefore, we recommend applying ¼” of water every two to three weeks trying to limit damage during dormancy. We’re still unsure how well TTF will survive in summers like this, but the
expanding acreage of TTF use over the last few years will give us a better idea after this summer.

Regardless of the species, keep all traffic (including mowing) off dormant areas. Even foot traffic will potentially damage the crowns and decrease survival.

Zac Reicher, Professor of Turfgrass Science, zreicher2@unl.edu, turf.unl.edu