Everything to Know About Kentucky Bluegrass

For many lawn owners in the Northern half of the United States, Kentucky bluegrass (Poa pratensis) is synonymous with the ideal lawn, and for good reason. When given its preferred growing conditions and proper care, this grass produces a lush, dense, and durable lawn that lives up to its historic reputation. Part of the charm of a healthy Kentucky bluegrass lawn is its rich emerald to blue-green color. Add to that its medium to fine texture and a Kentucky bluegrass lawn is both beautiful to look at and comfortable for bare feet and outdoor activities. 

Kentucky Bluegrass At A Glance

• cold-season grass with excellent winter hardiness
• prefers sun, limited shade tolerance
• suitable for northern lawns from coast to coast
• will go dormant if subjected to heat- and drought conditions for a lengthy time
• moderate water and maintenance requirements
• dense, traffic-tolerant growth
• some varieties vulnerable to stress damage

Kentucky Bluegrass Basics

Often referred to in the grass industry by its initials KBG, Kentucky bluegrass quickly rose to become a premier lawn grass throughout much of the country. While the state of Kentucky may be known as the “Bluegrass State,” Kentucky bluegrass did not actually originate there. Like many common turf grasses in the United States, this widely used grass is native to Europe and northern Asia (1).  Its first use in the U.S. was as a pasture grass in locations such as Kentucky, where it still covers the state’s well known gently rolling hills. KBG is what is known as a perennial, cool-season lawn grass. This means it comes back year after year and grows most vigorously during the cool seasons of fall and spring. KBG has the greatest cold hardiness of all the common cool-season lawn grasses (2). It is used most extensively in northern climates where moderately warm summers and cold winters follow with its natural preferences and growth cycle.

Characteristics and Traits of Kentucky Bluegrass 

Compared to tall fescue, traditional Kentucky bluegrass varieties have relatively shallow roots, which typically lead to lower tolerances for heat and drought (3). Historically, this has restricted the widespread use of KBG south of the climatically challenging ‘transition zone’, where higher heat and humidity favor warm-season grasses, such as Zoysia and St. Augustine grass. 

Unlike bunch-forming grasses, such as tall fescue and ryegrass, Kentucky bluegrass is a true self-spreading, sod-forming grass. Once established, it spreads readily by using underground stems (known as rhizomes) to form a dense and thick turf. This aggressive growth habit gives KBG the capacity to recuperate quickly from damage. Depending on your grass growing region and your lawn care goals, Kentucky bluegrass may be a perfect choice for you. As with other cool-season grasses, Kentucky bluegrass growth slows significantly during hot summer months. During extreme heat or extended drought, the grass will go dormant. However, it recovers quickly with irrigation and a return to normal conditions.

KBG establishes easily from seed, but it germinates more slowly than some other cool-season grasses. Fast-growing perennial ryegrass, for example, germinates in one-third the time of Kentucky bluegrass (1). Kentucky bluegrass prefers full sun, but some varieties can do well in lightly shaded areas. Look on the seed tag label of many grass seed mixes, including shade and sun & shade mixes, and you’ll find KBG varieties mixed with other cool-season grasses. Fast-greening perennial ryegrass and shade-tolerant fescues complement Kentucky bluegrass’s strengths to create versatile, lush, cool-season lawns. Durable KBG is also a regular component of seed mixes for athletic fields. 

Benefits and Characteristics

Kentucky bluegrass seed is better adapted to high foot-traffic and compacted soil. This makes the grass ideal for yards with children and dogs, park areas and sports fields. For the most part, Bluegrasses have the ability to recover from injury and disturbance due to their spreading rhizomes. This also gives them excellent winter hardiness. When properly watered during its growing seasons, bluegrass will grow back and fill-in after freezing, drought and periods of high-traffic.

Kentucky bluegrass matures into a beautiful, sod-forming turf with a fine texture and blue-green blades that form dense, spreading mats. Regular mowing will help bluegrass become thick, lush and uniform lawns.

Kentucky Bluegrass Lawn Care: 

Higher Maintenance, Higher Reward

While Kentucky bluegrass is lovely for many reasons, it can not achieve its full beauty on its own. This grass actually requires a relatively high level of maintenance to look its absolute, but the results of the extra tender loving grass care can be worth it. 

With Kentucky bluegrass and other cool-season lawn grasses, the best time to plant seed and do major lawn maintenance is during early fall, as KBG growth progress is at its peak. Because of KBG’s rhizomatous growth, the grass develops thatch easily, which can add to drought stress and potential for disease. Depending on your mowing and care practices, your KBG lawn may need dethatching every year or two.

Wise water management is essential for Kentucky bluegrass lawns. Deep, thorough irrigation helps encourage deep root growth, while shallow, frequent watering discourages proper growth. During normal weather, a typical KBG lawn needs at least 1 inch of water weekly from irrigation or rainfall. During warmer weather and in the transition zone, 2 inches or more per week may be needed (1). While the relatively shallow roots of traditional KBG varieties historically required more water than tall fescue or most warm-season counterparts in similar situations, modern developments have greatly improved water efficiency.

Like other cool-season grasses, Kentucky bluegrass should be mowed higher than warm-season grasses. Warm-season Bermudagrass, for example, is routinely kept near 1 inch tall, but KBG should be mowed to 2 to 2 1/2 inches high. During periods of high heat and lower rainfall, recommended KBG mowing heights increase to 3 to 4 inches (1).

Kentucky bluegrass lawns typically require more fertilizer than tall fescue and other grasses. In alkaline soils, blades can lose their rich green color due to pH-induced iron deficiency. The optimal soil pH for KBG lawns is near 5.8 to 7.0. (2) Regular soil testing every three to four years can help you maintain a healthy pH balance and rich KBG color with the help of quality lawn fertilizers, soil amendments and mineral supplements (3).

While this might seem like a lot of maintenance items to keep up on, as we’ve shown the benefits of KBG can definitely outweigh the time and energy required to keep the grass at its peak. 

Soil, Sun and Moisture Factors

Kentucky bluegrass seeds will tolerate limited shade but grow best in full sun. Some varieties of bluegrass have been bred to be more tolerant of shading, but dense shade is a limiting factor to the vigor of a bluegrass lawn. KBG requires well-drained soil and consistent moisture for optimal health and beauty (3). Due to shallow roots, bluegrasses will quickly go dormant if subjected to extended drought or under-watering.

At a Glance: Planting and Management Tips for Kentucky bluegrass

• Mow at 1.5 – 2.5 inches.
• For optimum performance, mow relatively high, especially during the warm months.
• Fertilize using 4 – 6 lbs. nitrogen/1000 sq. ft. per year during the period of active growth (end of February – end of May; October – November).
• Plant with seed or use sod.
• If seeding, seed at 2 – 3 lbs. seed/1000 sq. ft.
• Water frequently, every 1 – 3 days during the summer because of the shallow root system.
• Susceptible to most turfgrass diseases and insects
• Low drought tolerance

Still unsure of how to best care for your Kentucky Bluegrass lawn? Check out your state’s agricultural extension office for helpful tips and soil testing kits that will help you determine your best lawn care plan.

If you live in the northern or central United States and your lawn needs call for a durable and wear-resistant cool-season lawn that can grow thick and lush, Kentucky Bluegrass may be the perfect solution providing you seasons of turfgrass.

Sources:

1. Duble, R.L., “Kentucky Bluegrass,” Texas A&M Agrilife Extension.

2. Patton, A. and Boyd J., “Choosing a Grass for Arkansas Lawns,” University of Arkansas Cooperative Extension.

3. Cook, T., “Kentucky Bluegrass, Poa Pratensis L.,” Oregon State University Department of Horticulture.

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