Do you start to resent your lawn this time of year? That lush green grass from spring has disappeared and withered into dried brown masses. With a Kentucky bluegrass lawn this slowdown is a natural part of the life cycle, typical of any cool season grass.

Let’s review some Kentucky bluegrass characteristics and principles of care. Kentucky bluegrass is a common, non-native turfgrass along the Front Range. While it may require more water and may have more frequent insect problems than other varieties, it does have excellent heat and cold tolerance with good drought resistance and it tolerates clay soil well.

Mowing Kentucky Bluegrass
Mowing a lawn too short reduces the drought resistance and heat tolerance. It also increases opportunities for weeds, lawn diseases and insects. For best results, the turf should be left at two and one-half to three inches year round. During mowing, obey the “one-third rule,” removing only the top third of the grass. Applying these principles, mowing may be required every three to five days in the spring, but perhaps only at seven to ten day intervals in July and August. If possible, clippings should be mulched back onto the lawn. Contrary to popular belief, mulching does not build thatch. It returns beneficial nutrients to the lawn. Be sure to mow with a sharp blade to avoid tearing the grass.

Fertilizing Kentucky Bluegrass
Less fertilization is needed when clippings are returned to the lawn. If spring green-up and growth are satisfactory in an established lawn, fertilization may be delayed until May or June. Fertilization is not necessary from July to early August. Fertilizing in early fall (mid-August to mid-September) and late fall (early October to early November), while the grass is still green, will help the grass winter well and green up early in the spring. It will also aid in root growth. When doing fall fertilization it is important to remember that nitrogen is the key component. A winterizing fertilizer may be used, or a fertilizer containing quickly available nitrogen such as ammonium phosphate, ammonium sulfate or ammonium nitrate. These work well with lower temperatures of fall.

Watering Kentucky Bluegrass
Many factors contribute to the amount of water that needs to be applied to a Kentucky bluegrass lawn. The clay soil of the Front Range holds and absorbs moisture well. When a lawn looks thirsty, a common mistake is to increase the watering time. It is more effective to water for short intervals more frequently. Using a standard home delivery system with pop up sprinkler heads, eight to ten minutes is about the optimal time any one turf zone should run. The full cycle may need to be repeated two or more times depending upon rain, humidity, wind and heat in the environment. It is also important to know the effectiveness of your sprinkler system. Many home systems operate significantly under what is considered “effective.” The City of Fort Collins offers a free audit, within city limits, to determine the effectiveness of sprinkler systems. To request information, or an audit, call 970-221-6700. Or, if you’d prefer to do an audit yourself, read CSU Extension Fact Sheet #7.239, “Operating and Maintaining a Home Irrigation System.”

Kentucky bluegrass may require one to two inches of water a week when it is hot, dry and windy. Pop up sprinklers can deliver 1.25 inches of water per hour when they are at an 80 percent effectiveness level. Clay soil can take in 0.25 inches per hour. Three, eight minute-per-zone cycles will deliver a half inch of water if the system is operating effectively. Watering at this rate three times a week should deliver one and a half inches, with enough time for the water to soak in and not run off.

Following these principles will help contribute to a healthier lawn that is more resistant to disease and weeds.

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

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This page updated:  July 18, 2007