Kentucky bluegrass is a popular cool-season grass prized for its attractive emerald to blue-green color and fine texture. As a staple in northern climates, it grows most vigorously in the spring and fall when temperatures are moderate. Homeowners frequently misunderstand the grass’s ability to handle dry weather, often assuming it is a poor choice for low-water landscapes. While Kentucky bluegrass is not drought-tolerant in the traditional sense, it possesses a highly effective, built-in survival strategy that makes it remarkably resistant to death from drought.
Kentucky Bluegrass’s Drought Strategy
Kentucky bluegrass is not drought tolerant in the sense of remaining green and actively growing without sufficient water. When water is scarce, the plant’s natural response is to enter summer dormancy, stopping growth to conserve moisture. The grass blades will turn a straw-brown color, which often leads homeowners to believe the lawn is dead. This process is a survival mechanism, making the grass highly drought-resistant. The crown and the underground stems, known as rhizomes, remain alive. Rhizomes act as storage organs, holding energy and moisture until favorable conditions return. Kentucky bluegrass can survive in this dormant state for up to two months without irrigation, though this duration varies based on soil type and environmental factors.
Root Structure and Water Needs
Kentucky bluegrass has a relatively shallow root system, with the majority of its roots concentrated in the top 6 to 10 inches of soil. Compared to other turf species, this shallow depth makes it highly susceptible to surface drying, meaning it loses access to moisture quickly during dry spells. The grass requires a consistent water supply, often needing between 1 to 2 inches of water per week to maintain its vibrant green color and active growth. When the topsoil dries out, the plant cannot access deeper moisture, triggering the drought-induced dormancy response. The resilient, deep-running rhizome network ensures the plant’s survival.
Preparing the Turf for Dry Conditions
Proactive cultural practices implemented before the onset of summer heat and drought can significantly delay the need for dormancy.
Mowing Height
Adjusting the mowing height is an effective preparatory step. Raising the cutting height to between 3 and 4 inches shades the soil, which reduces water evaporation and helps keep the crown of the plant cooler. Taller grass also encourages the development of a deeper root system, improving the plant’s ability to withstand dry periods.
Aeration
Improving the soil’s ability to absorb and hold water is accomplished through aeration. Core aeration removes small plugs of soil, relieving compaction and allowing for better water infiltration and air exchange to the root zone. This practice, ideally performed in the fall, helps ensure that rainfall or irrigation water reaches the roots rather than running off the surface.
Fertilization
Fertilization must be managed carefully. Applying too much nitrogen fertilizer in late spring or early summer stimulates excessive top growth, which increases the plant’s water demand during the hottest part of the year. Instead, a slow-release nitrogen fertilizer program focusing on spring and fall applications is recommended to build strong roots without pushing water-hungry leaf growth during heat stress. This balanced approach strengthens the turf, making it less prone to disease and stress when dry conditions arrive.
Reversing Dormancy and Recovery
When a drought begins, the lawn can either go fully dormant or be maintained with minimal watering. If full dormancy is permitted, the lawn can survive for up to eight weeks without intervention. For those who wish to ensure survival during an extended drought, approximately 0.5 inches of water every two to four weeks is sufficient to keep the crowns and rhizomes hydrated. It is important to avoid applying too much water to a dormant lawn, as this can signal the grass to break dormancy, leading to immediate stress if water is not consistently available. Once temperatures cool or regular rainfall returns, the process of recovery can begin. The best time to resume normal watering is in the fall, using a deep, infrequent schedule to encourage new root growth. Following the return of favorable conditions and proper watering, the lawn will begin to green up from the protected crown and rhizomes. The expected time frame for a successful recovery typically ranges from one to three weeks. Overseeding damaged or thinned areas in the fall can accelerate the process of restoring a dense turf.