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Difference Between St. Augustine & Kentucky Bluegrass

By Jeff Farris ; Updated September 21, 2017
The fort in St. Augustine, Florida is surrounded by its namesake turfgrass.
Castillo de San Marco - ancient fort in st. augustine florida image by Sakala from <a href='http://www.fotolia.com'>Fotolia.com</a>

Kentucky bluegrass (Poa pratensis) and St. Augustine grass (Stenotaphrum secundatum) have little in common other than being green and widely used for lawns. Their cultural requirements, uses and appearance couldn't be more divergent.


Kentucky bluegrass is a cool-season grass that grows best when soil temperatures are around 60 degrees F. It cannot survive in the heat of the South. It over-winters well, even in even the harsh winters of Canada. On the other hand, St. Augustine thrives on heat, and with the exception of one carefully developed cultivar, cannot survive the winters north of South Carolina.


St. Augustine has a coarse, wide blade width, dense turf development and dark green color. Kentucky bluegrass has a medium to fine blade width (dependent on cultivar), with a dark green color and dense development.

Traffic Tolerance

Kentucky bluegrass recovers from traffic well, which explains why it is widely used for sports fields in the Northeast and Upper Midwest, notes Penn State University. St. Augustine does not handle traffic well at all. St. Augustine is favored by southern homeowners who value appearance more than wear tolerance (Bermudagrass is the sports turf of the South).


St. Augustine should be kept relatively long--2 1/2 to 3 1/2 inches, whereas Kentucky bluegrass should be kept from 3/4 to 2 1/2 inches. In both cases, no more than one-third of the blade length should be cut in any one mowing.

Water Requirements

Where rain is infrequent, St. Augustine needs careful irrigation to survive. Kentucky bluegrass survives long periods of drought by going dormant in the summer. It greens up quickly in response to either rainfall or irrigation, notes Texas A&M University.


Kentucky bluegrass needs 2 to 6 lbs. of nitrogen per year over three applications, with the higher rate needed by newly planted lawns. Applications should be timed for late spring, once the normal spring growth spurt has slowed, and then in September and October. St. Augustine needs a monthly application of 1 lb. per 1,000 square feet during the growing season, which is normally March through September.


About the Author


Jeff Farris has focused on instructional communication since 1980. His work includes instruction manuals, promotional materials, video scripts and web content on a variety of hands-on topics. His work has been published in "Scuba Diving" magazine as well as several websites. He holds a Bachelor's degree in marketing from the University of Missouri.