This summer's hot, dry weather has been stressful for trees, shrubs, annuals, perennials, fruits, and vegetables. The hot, dry conditions have also caused Kentucky bluegrass and other cool-season grasses to turn brown and go dormant.
Dormancy is a natural survival mechanism for Kentucky bluegrass and other cool-season grasses. During extended dry periods, turfgrass foliage will cease growth and turn brown. While the foliage is dead, the turfgrass crowns and roots remain alive.
Generally, turfgrass can remain dormant for several weeks without suffering significant damage. However, lawns can die in a prolonged drought. To improve the survival odds for dormant lawns, apply (if possible) one-quarter-inch of water per week. This will not green up the lawn but should keep the turfgrass crowns hydrated (alive) until rains eventually fall.
Fertilizing a dormant lawn will not harm it. However, the turfgrass may not receive the full benefit of the fertilizer application. In Iowa, spring, mid-September, and late October/early November are the best times to fertilize lawns.
Broadleaf herbicides are most effective when applied to weeds that are actively growing. Because of the dry conditions, most broadleaf weeds are also exhibiting stress symptoms (curled or wilted leaves). Applications of granular or liquid broadleaf herbicides are likely to be ineffective as most broadleaf weeds are not active growing. In Iowa, mid-September to early November is the best time to apply a broadleaf herbicide to lawns.
The application of standard lawn care treatments to dormant lawns by lawn care professionals will not harm the turfgrass. In fact, the turf will likely benefit from the treatments when it emerges from dormancy. Additional information from a study which examined the effects of lawn care treatments to dormant lawns can be found in a posting in the Iowa Turf Blog from July 20, 2012.
If possible, avoid moderate to heavy foot or vehicular traffic on dormant lawns. Moderate to heavy traffic will likely damage the turfgrass crowns. Damaged plants may not fully recover when rain returns.
It's advisable not to allow lawns established in 2011 and 2012 (either by seed or sod) to go dormant. The root systems of recently established lawns are not as extensive as older lawns. Newer lawns may not survive dormancy. If possible, water recently established lawns on a weekly basis. Apply 1 inch of water per week in single application or one-half inch every 3 to 4 days.