AMES, Iowa — The drought of 2012 has taken a toll on many lawns across Iowa. The crispy brown lawns of August have begun to recover with September rains, but all is not well.
Kentucky bluegrass is the most dominant grass in Iowa lawns, according to David Minner, turfgrass specialist with Iowa State University Extension and Outreach. “Most summers when water is lacking the turfgrass leaves turn brown but the below ground crowns, buds and rhizomes survive in a dormant condition only to produce new growth when water returns,” Minner said. “We have become very accustomed to letting the lawn turn brown in the summer and then watching it re-green in the fall.”
Minner said the problem with this strategy is that summer dormancy is not an absolute guarantee that the grass plants will survive. Most of the time non-irrigated lawns turn dormant in late July after about two to three weeks with no water. They can remain brown and dormant, but alive, for approximately four to six weeks without water. Again, these are general statements and estimates, not absolute values. It is important to remember that the dormancy factor in Kentucky bluegrass also has its limit, and it was reached in many lawns across Iowa in 2012.
Minner has been driving through many new and older neighborhoods in Iowa to get a feel for the amount of turf damage caused by the drought. He has found that older neighborhoods where trees shade the ground don’t seem to have as much turf loss. Lawns with hills and slopes, especially those facing the south lost substantial turf. Thatchy and sandy soil lawns left un-irrigated also experienced severe turf loss.
“The green grass of watered lawns is easily discernible from the dormant lawns that are now struggling to recover,” he said. “My travels across Iowa indicate that most neighborhoods have approximately 25 to 50 percent of the lawns showing some degree of turf loss from the drought and of the injured lawns approximately 25 to 50 percent of the turf in each lawn has been killed.”
The bad news is that some of homeowners are now dealing with dead grass and no amount of watering or rain will make it recover. In fact, the dead areas of the lawn that are not repaired this fall will likely be invaded by weeds next year. The good news is that September is the perfect month to renovate the lawn or at least reseed the damaged areas.
“Don’t delay, if the grass is brown it’s probably dead (not dormant) and won’t recover and you will have missed the best seeding window to re-establish the lawn,” Minner said. He outlines renovation and reseeding steps in the article Drought Damaged Lawns Need Help; the article was recently posted on the ISU Extension and Outreach Dealing with Drought website under the home and lawn tab.
Minner points out that management practices in the fall and spring determine the drought tolerance of the lawn in summer. To reduce the need for irrigation, a lawn management program should maximize root volume and depth in preparation for summer drought. By the time summer rolls around, there is little to do to help a lawn except mow and irrigate properly. Management practices that prepare a lawn for drought and tips on water conservation while watering a lawn are included in the full article at https://www.extension.iastate.edu/topic/recovering-disasters.
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PHOTO: There is a stark contrast between the irrigated lawn on the left and the non-irrigated, nearly completely dormant lawn on the right.