Walk through your lawn and note the color of the grass. Healthy grass ranges from light green to deep green, while some grasses have a blue-green color. Also feel the grass to determine whether its texture is rough and course, soft and fine, or in-between the two. Determine whether the blades are wide or narrow.
Determine whether you live in a cool season grass environment (northern United States). In such zones, winters are cold while summers are hot, with some rain. Grass that grows in such areas is Kentucky 31, Kentucky Bluegrass, Hard Fescue, Fescue Tall, Fescue Red, Chewings Fescue, Fine Fescue, Ryegrass, Perennial Rye, Titan, Turf-type Tall Fescue, Zoysia out or Thermal.
Determine whether you live in a warm season grass environment (southern United States). Such areas have mild winters with very hot summers, and little rainfall. Grass that grows in such areas includes St. Augustine, Bermuda, Buffalo, Zoysia, Thermal Blue, Bentgrass, Bahia, Centipede, Carpet and Palmetto St. Augustine.
Determine whether the grass grows in full shade to partial shade. Full-shade loving, cool season grasses include Annual Bluegrass, Rough Bluegrass and Fine Fescue. Creeping Bentgrass, Kentucky Bluegrass, Tall Fescue and Perennial Rye are cool season grasses that require medium shade, while Zoysia, Centipede and St. Augustine are warm season grasses that require medium shade to grow and spread.
Determine whether you live in a transition zone (central United States). These includes the states of Kentucky, Virginia, Tennessee, Missouri, Ohio, Kansas, Illinois and Arkansas. Kentucky Bluegrass, Annual Rye, Perennial Rye, Turfgrass, Zoysia or Turftype Fescue are grasses that grow here.
Pull out several grass blades and study them in detail. Note down features such as color, texture and blade width. Also note the rate at which it grows and the amount of water you give it weekly.
Consult an online grass identification guide such as those listed in the Resources to narrow your study. These sites provide easy-to-follow color map of the United States highlighting cool, warm and transition zones, along with visual aid of types of grass that grows in each zone. Use this information along with your notes and samples for a quick and definite identification of the grass type.