The Cool-season Turfgrasses: Identification

Turfgrass Identification

Also, there are several pesticides that are safe to apply to some turfgrass species, but not others. If a herbicide that is safe only on Kentucky bluegrass is applied to a fine fescue lawn, serious damage could result and you may have to replace the lawn. Before making important turf management decisions, be sure that you can identify the turfgrass species present at the site.

Identification of the cool-season turfgrass species is not difficult once you learn how to recognize a few plant structures and some subtle features associated with those structures. Descriptions of the plant parts used in identification of turfgrasses are provided in the following paragraphs. Some of these have been discussed in "The Cool Season Turfgrasses: Basic Structures, Growth and Development". Diagrams and descriptions of identifying features of cool-season turfgrass species are provided in this section.

Vernation

Vernation is a term used to describe how the youngest grass leaves are arranged in the shoot (inside of the leaf sheath between the collar region and the crown). Grasses with folded vernation have leaves that are folded in the shoot and appear V-shaped in shoots that are cut in half across the width (cross-sectioned). Leaves with rolled vernation are circular or "rolled" in the shoot and do not have folds (Figure 1). To determine if a grass specimen has folded or rolled vernation, hold the shoot between your thumb and index finger and roll it. If it rolls like a straw, it has rolled vernation, if it lies flat and has edges, it is folded. You can also determine vernation by cutting a cross-section of the shoot just below the collar region and looking at the leaf arrangement.

Figure 1. Examples of folded and rolled vernation

Leaf Blades

Leaf blades have certain characteristics that are useful in turfgrass identification. Some species have leaf blades with a single prominent vein running lengthwise down the center of the blade. Others have many equal-sized veins (no dominant mid-vein) running lengthwise over the entire width of the leaf blade (Figure 2). A few species have both a prominent mid-vein and many smaller veins oriented lengthwise over the entire width of the blade. Certain turfgrass species have a glossy appearance on the underside of the leaf blade, whereas others are dull (not glossy). Some turfgrasses have leaf blades that terminate in a flat point, whereas others have leaf blade tips that are keeled (sometimes referred to as a 'boat-shaped' tip) (Figure 2).

Figure 2. Leaf blade with prominent vein running lengthwise in center of blade (a) and one with many equal-sized veins (no dominant mid-vein) running lengthwise over the entire width of the blade (b). Diagram of turfgrass leaf tips showing keeled, flat, and pointed.

Ligules and Auricles

Ligules are membranous or hairy tissues located at the junction of the leaf blade and leaf sheath. Depending on the species, ligules can be membranous, a fringe of hairs, or absent (Figure 3A). None of the cool-season turfgrasses have ligules that appear as a fringe of hairs, but this feature is common on many weed grasses and most warm-season turfgrasses. Auricles are slender extensions of the collar and are located at the junction of the leaf blade and leaf sheath. They can be long and clasp around the stem or shoot, small or rudimentary, or absent (Figure 3B).

Figure 3. (A) In turfgrasses, ligules may be membranous, hairy, or entirely absent. (B) Auricles may be long and clasping, small or rudimentary, or absent.

Growth Habit

Growth habits of cool-season turfgrasses are either rhizomatous (producing rhizomes), stoloniferous (producing stolons), or bunch type (a species that does not produce rhizomes or stolons -- only tillers). In some cases, the growth habit of turfgrasses can be useful in identification. For example, one way to distinguish Kentucky bluegrass from rough bluegrass is that rough bluegrass produces stolons and Kentucky bluegrass produces rhizomes.

Figure 4. Rhizomatous, bunch, and stoloniferous growth habits.

The Seed Head

Although seed head characteristics are among the best identifying features of turfgrass species, they are often removed by mowing. Where seed heads can be observed, they are classified as panicle types, spike types, or racemes. Recognizing differences among these seed head types can be useful in distinguishing among the cool-season turfgrass species.

Figure 5. Three types of turfgrass seed heads: panicle (left), spike (middle), and raceme (right)..

Identifying Features of Cool-Season Turfgrass Species

Kentucky bluegrass

• Folded vernation
• Prominent mid-vein (no other veins noticeable), leaf blade dull underneath, keeled leaf tip
• Auricles absent
• Short, membranous ligule
• Rhizomatous growth habit
• Panicle-type seed head

Kentucky Bluegrass

Rough bluegrass

• Folded vernation
• Prominent mid-vein (no other veins noticeable), leaf blade glossy underneath, keeled leaf tip
• Auricles absent
• Short, membranous ligule
• Stoloniferous growth habit
• Panicle-type seed head

Rough Bluegrass

Perennial ryegrass

• Folded vernation
• Prominent mid-vein with many smaller veins oriented lengthwise over the entire width of leaf blade, leaf blade glossy underneath, keeled leaf tip
• Small, rudimentary auricles
• Short, membranous ligule
• Bunch-type growth habit
• Spike-type seed head

Perennial Ryegrass

Annual ryegrass

• Rolled vernation
• Prominent mid-vein with many smaller veins oriented lengthwise over the entire width of leaf blade, leaf blade glossy underneath, keeled leaf tip
• Long, clasping auricles
• Short, membranous ligule
• Bunch-type growth habit
• Spike-type seed head

Annual Ryegrass

Fine fescues

• Folded vernation
• Very narrow, folded leaf blades -- in most cases, veins not visible, leaf blade dull underneath, keeled leaf tip
• Auricles absent
• Short, membranous ligule
• Bunch-type or rhizomatous growth habit
• Panicle-type seed head

Fine Fescues

Tall fescue

• Rolled vernation
• Blades have many equal-sized veins (no dominant mid vein) running lengthwise over the entire width of the leaf blade, leaf blade dull underneath, pointed leaf tip
• Auricles absent
• Short, membranous ligule
• Primarily bunch-type growth habit, sometimes short rhizomes are present
• Panicle-type seed head

Tall Fescue

Creeping bentgrass

• Rolled vernation
• Blades have many equal-sized veins (no dominant mid vein) running lengthwise over the entire width of the leaf blade, leaf blade dull underneath, pointed leaf tip.
• Auricles absent
• Tall, membranous ligule
• Stoloniferous growth habit
• Panicle-type seed head

Creeping Bentgrass

Prepared by Peter Landschoot, professor of turfgrass science