Gardening 101: Kentucky Bluegrass

Kentucky Bluegrass, Poa pratensis

Turf grass is a quintessential feature of the American landscape. Close your eyes, think of the phrase “Kentucky bluegrass,” and you see in your mind’s eye suburban front lawns, backyards with volleyball nets, the whirr of the gas-powered lawn mower that your next-door neighbor has fired up too early on a Saturday morning.

“The domestic front lawn is a typically American landscape feature. Lawns can be found in all parts of the country, from New England to Florida to California. Houses in Phoenix have front lawns, as do houses in Chicago and Atlanta,” writes Virginia Scott Jenkins in The Lawn: A History of an American Obsession. “But this has not always been the case.”

In fact, lawns are an idea that Americans borrowed from Europe. “Lawn grasses are not native to this continent,” writes Jenkins. In the late 18th century, wealthy Americans saw lawns in England and France (Versailles was perhaps the first palace to have a postage-stamp square of velvety turf). Seeds for meadow grasses–including Poa pratensis (Kentucky bluegrass)–were imported from Europe, Asia, and North Africa, where they grow wild.

After the 19th-century invention of the lawn mower, Americans came to rely on turf grasses to carpet garden spaces, with the rest of the plants (shrubs, perennials flowers, specimen trees–consigned to the perimeter of the property.

Nowadays climate changes are influencing landscape styles—particularly in regions such as the Southwest and California, where water is a precious commodity. “Kentucky bluegrass (Poa pratensis) is a turf grass species that was substantially a bigger part of home lawns in the ’70s and ’80s than it is right now,” notes the University of Missouri’s Integrated Pest Management program. “Yes, we still see Kentucky bluegrass being used in home lawns, but more so in a mixture with turf-type tall fescues. Hot, droughty summers of the past decade have transitioned many home lawns from a blend of bluegrasses to mixtures with other species. Kentucky bluegrass is not as deeply rooted as tall fescue and therefore has a tendency to go dormant faster than tall fescues.”

Will the soft beauty of un-mown meadow grasses and environmentally friendly clumps of feathery ornamentals change our idea of what constitutes a” lawn?” Read on to learn more about Kentucky bluegrass:

Poa pratensis has soft, thin blades and spreads by rhizome to create a thick mat. It’s the perfect texture for supporting a picnic blanket.

Depending on your climate, your lawn will likely be made up of a mix of cool-season turf grasses such as Kentucky bluegrass and fescues, or a warm-weather grass such as St. Augustine grass.

The trouble with turf is that it requires a lot of water to thrive. Kentucky bluegrass, for instance, can require from 1.5 to 2.5 inches of water a week depending on the season (it needs more water in hot, summer months).

With growing environmental concerns and the prospect of continuing climate change, landscape designers have in recent years shied away from turf in favor of lawn alternatives that require fewer natural resources. “The suburban romance with groomed grass turf is over,” writes our contributor Janet Hall. “The good news for those who still want a field of green is the abundance of lawn substitutes that can accommodate foot traffic, pet traffic, and rounds of lawn games.” See ideas in Fields of Green: 5 Favorite Lawn Substitutes.

Poa pratensis is known in Europe as meadow grass. Here in the US, where it is called Kentucky bluegrass, how did this imported plant earn a hometown nickname? Kentucky bluegrass–and other species of Poa grasses–thrive in Kentucky’s climate, where it quickly spread after introduction in the 19th century. When it is not mowed, Kentucky bluegrass will develop purplish-blue seed heads in a meadow, which from a distance will look like a hazy blue swath.

Cheat Sheet

• If you don’t mow it, Kentucky bluegrass will grow to a height of 3 feet and develop feathery, tufted flowers. Treat it like a meadow grass, as shown above, at the edge of a lawn.
• Is there an environmentally friendly strain of Kentucky bluegrass? “Many of the newer, improved varieties are being developed for better drought tolerance, disease resistance, and low maintenance,” notes the University of Missouri. (Cultivars including ‘Moonlight’, ‘Prosperity’, and ‘Diva’ “demonstrated significantly better drought tolerance” in a recent study led by researchers in the horticulture department at the University of Arkansas.)
• A proper lawn-maintenance program including aerating, seeding, and fertilizing will make turf grass healthier and less needy. See more in Your First Garden: What You Need to Do in Fall for a Lush Lawn in Spring.

Keep It Alive

• A cool-weather grass, Kentucky bluegrass thrives in USDA growing zones 3 to 9.
• Poa pratensis likes moist, well-drained soil and sun or partial shade.
• When mowing, remove no more than one-third of the height of grass blades.

Read more in Kentucky Bluegrass: A Field Guide to Planting, Care & Design in our curated guides to Grasses 101. See more turf grass options (and alternatives):

• Zoysia Grass: A Field Guide to Planting, Care & Design
• 10 Easy Pieces: Grass Block Pavers
• St. Augustine Grass: A Field Guide to Planting, Care & Design
• Before & After: From a Blank Canvas to a Golden Garden in a London Suburb
• 10 Garden Ideas to Steal from Superstar Dutch Designer Piet Oudolf