St. Augustine and Bermuda grass are perennial grasses grown in the southern parts of the U.S. Both these warm-season grasses prefer full sun or partial shade. St. Augustine is native to Africa, Caribbean and the Mediterranean, while Bermuda grass, also called Couch grass, Bahama grass or Devil's grass, is from Europe. The grasses differ from one another in many ways.
St. Augustine grass has medium to coarse texture, with a deep-green to almost bluish-green color. It has broad grass blades and flat stems. Bermuda grass has medium to fine texture and dark green blades. It also has tall purple shoots. St. Augustine lawn grass needs to mowed down to a height of 1 to 3 inches, while Bermuda grass cannot grow very high, which is why gardeners in the South mow it close to the ground so it forms a low-lying, dense turf.
St. Augustine grows in full sun to partial shade, is salt-resistant and survives poor soil conditions. It tends to thin under dense shade and gets damaged easily if temperatures fall below 25 degrees F. Below-freezing temperatures cause the grass to die. Bermuda grass grows in full sun and is salt- and drought- resistant. It goes dormant at the first drop of temperature but regains its color when temperatures rise again. A few cold-resistant verities of Bermuda grass are available.
St. Augustine grass has moderate to excellent durability, and withstands some amount of foot traffic. Bermuda grass is highly durable and withstands high-traffic areas.
St. Augustine grass thrives in the humid and moist climates of tropical and subtropical regions. Bermuda grass grows in hot tropical and subtropical areas, but some varieties grow in transition zones between cool-season and warm-season grasses.
St. Augustine is commonly grown in domestic lawns or low-traffic areas as it cannot withstand heavy foot traffic well. Bermuda grass, on the other hand, is much stronger and withstands large amounts of foot traffic, which is why it is commonly grown in golf courses, sports fields, parks and general utility turfs in southern U.S.
Despite its strength, St. Augustine grass is highly susceptible to lawn disease and pests. These grasses succumb to their death when they fall victim to a viral disease known as St. Augustine Grass Decline. St. Augustine grass usually has excessive thatch buildup while Bermuda grass develops moderate thatch buildup. However, it is often considered invasive because it grows new plants easily by shoots. It overtakes other plants, spreads into flowerbeds easily and is very difficult to remove if you want to grow another variety.