What to Know About Kentucky Bluegrass and How to Care for It

Closeup of lawn with Kentucky bluegrass.

Catherine McQueen/Getty Images

Kentucky bluegrass (Poa pratensis) is one of the most beautiful lawn grasses. True to one part of its name, it can bear a relatively dark (bluish-green) color at times. But the other part of its name is a misnomer: It is native to Europe and northern Asia, not Kentucky.

Kentucky bluegrass is considered one of the cool-season grasses, making it one of the turf options for Northerners looking to start a lawn. But how would they go about selecting one type of cool-season grass over another? The best way to begin the decision process is to draw up a list of pros and cons for the respective choices. Read on for everything you need to know about Kentucky bluegrass, including pros and cons, care and maintenance, and seasonality.

Pros of Kentucky Bluegrass:

  • Withstands foot traffic well
  • Holds up to dog traffic, too
  • Is easy on bare feet due to its soft texture, making it a good choice around pools
  • Exhibits extreme cold-hardiness
  • Recovers well from stress (due to its vigorous rhizomes)

Cons of Kentucky Bluegrass:

  • Relatively high-maintenance: needs abundant watering, grass has poor water absorption because of shallow roots resulting in mud and water runoff
  • Not shade-tolerant
  • Not heat-tolerant
  • Not drought-tolerant (due to its shallow roots)
  • Invasive in parts of the United States, such as Northern Great Plains, and potentially crowds out other plants
Classification Poa pratensis
How It Spreads By rhizomes
Shade Tolerance Poor
Drought Resistance Poor
Foot Traffic Tolerance Good
Maintenance High
Mowing Height 2.5 inches in spring and fall, 3.5 inches in summer
Soil ph Slightly acidic to slightly alkaline
Soil Type Fertile, well-drained loam
Where It Grows Best Northern states
Lifespan Long-lived

What Is Kentucky Bluegrass?

Kentucky bluegrass is a perennial, cool-season lawn grass. It is a true grass, being a member of the Poaceae family. It is one of the most common types of grass grown in lawns in North America.

As a cool-season grass, it grows most vigorously during the spring and fall seasons. Kentucky bluegrass spreads via rhizomes to form a uniform sod. This growth habit distinguishes it from bunch-forming grasses, such as tall fescue (Festuca arundinacea). Whereas the tufts of the latter give a lawn a patchwork look, a lawn composed of Kentucky bluegrass forms a consistent, level surface. This makes it a great choice for lawns where sports will be played.

Planting Kentucky Bluegrass

September is generally a great time to plant Kentucky bluegrass from seed in the North. Its seed germinates best when the soil temperature is between 50 and 65 degrees Fahrenheit. By September, the soil has had all summer to warm up to these levels. Yet, unlike in summer, you won't have the scorching heat to contend with, which dries out the seed.

September also provides better conditions for you than planting the grass summer, which is important because, with all the prep work involved, you will be spending a lot of time in the yard on this project. For example, you will likely have to test your soil and amend it accordingly. Spring is also an acceptable time to start a new lawn, but be aware that the summer heat may come unexpectedly before your grass has had time to mature.

Kentucky bluegrass is slower to germinate than other cool-season grasses, so budget your time accordingly. It will take Kentucky bluegrass seed at least two weeks (and up to a month) to germinate, whereas other cool-season grasses can do so in a little more than one week. If your schedule doesn't give you the flexibility to be available for lawn care every day over such an extended period, this could influence your decision whether or not to start Kentucky bluegrass from seed.

Some homeowners prefer to start a lawn by laying sod. It provides instant results, but laying sod costs more. Other than that, the same factors are in play as with seeding. September is a great time to lay Kentucky bluegrass sod, with spring being the second-best time. Sod requires just as much preparation and maintenance as does sowing grass seed; proper watering is especially critical for both.

Grass Seed Mixes

Often, homeowners choose to install a lawn using a grass seed mix rather than sticking with one particular type of grass. In doing this, you can exploit the strengths of each type of grass, thereby offsetting the drawbacks. If a lawn area receives some shade, for example, a grass seed mix suitable for it need contain only one type of grass designed for shade; other types in the mix can offer strengths that the shade-tolerant species lacks.

Care and Maintenance of Kentucky Bluegrass

Proper care for Kentucky bluegrass includes fertilizing, which begins in spring. What your lawn craves most at this time is nitrogen, and, if you read the label on commercial products such as Scotts Turf Builder, you will see from the NPK ratio that nitrogen is the dominant element. If you have a problem with crabgrass, look for a product that includes a crabgrass pre-emergent herbicide. Applying fertilizer in spring is critical, but it is only the beginning: You should maintain a fertilizing schedule throughout the growing season if you want the best possible lawn of Kentucky bluegrass.

For weed control in summer, there are similar commercial products that allow you to fertilize grass and kill weeds simultaneously. Also, pay attention to insect control, for which there are both products to apply after the fact and preventive measures. Problem insects for lawns include:

But, along with watering, your main task in maintaining a lawn will be mowing it properly. Determining the correct mowing height answers, at the same time, the question of how often to mow. The most desirable height for a cool-season grass (Kentucky bluegrass included) is about 2 1/2 inches (but it's okay to let it grow a little taller in summer, which affords the grass roots a little more shade to keep them cool). Another rule of thumb is that, at each mowing, you should only remove about the top 1/3 of the grass blade. So a good time to mow lawns is when the grass is about 3 2/3 inches high.

Even if you've successfully weathered the fertilizing and pest control, the mowing and the watering, that your Kentucky bluegrass demands in spring and summer, your work still isn't over. In September you should be overseeding bare spots and patches of thin growth; you will have a better lawn for it next year. Later in the fall, you will need to rake fallen leaves off your lawn. Raking leaves is not just about aesthetics. Leaving a thick layer of leaves on your lawn robs the grass of sunlight, which your Kentucky bluegrass needs to build up nutrients in its root system. Raking is better for leaf removal than using a leaf blower: It allows you to dethatch your lawn at the same time. Finally, take steps to winterize your Kentucky bluegrass and get it ready for next year

  • Is Kentucky bluegrass hard to grow?

    Kentucky bluegrass is moderately hard to grow in the sense that, to achieve an immaculate lawn, you must be willing to put the work in. This means consistently and correctly performing such tasks as fertilizing, watering, and mowing.

  • Does Kentucky bluegrass like sun or shade?

    Grow Kentucky bluegrass in full sun for best results.

  • Will Kentucky bluegrass choke out other grass?

    Because Kentucky bluegrass spreads via rhizomes to form a dense sod, it is capable of crowding out less vigorous grasses over time. In addition, it is an extremely resource-intensive grass and will out-compete trees and other landscaping for nutrients.

Article Sources
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  1. Kentucky Bluegrass Invasion in the Northern Great Plains and Prospective Management Approaches to Mitigate Its Spread. The National Center for Biotechnology Information