Wednesday, July 23, 2008

Turf ID

Why Does Identifying Turfgrasses Matter?

Proper management of a turf area requires correct identification of the turfgrasses on a particular site in order to determine appropriate management practices like: proper mowing height and frequency, fertilization needs, irrigation, and if needed pesticides. Often the turfgrass species that are present are not necessarily what was originally planted but are reflective of the cultural practices and prevailing growing environment. Together these two factors influence shifts in the turfgrass community of one species over another, which may affect management practices.

Identifying a Turfgrass:
Identifying turfgrasses is much like solving a puzzle. Several pieces or identifying characteristics are viewed, their exact nature determined and the species identified. Unfortunately, no single characteristic or feature alone is sufficient to determine with complete certainty a particular turfgrass species. Grasses have their leaves arranged in ranks of two (see photo/diagram), and a ligule is often present.
Determining Vernation:
The newest leaf of a turfgrass plant always arises from the center of the shoot and can be located in the newly expanding bud leaf/shoot. The orientation of newly emerging leaf is called Vernation. This characteristic is difficult to determine on older leaves because they are located on the outside of the shoot and have expanded making Vernation difficult to determine. For most turfgrasses, the Vernation will either be rolled or folded.
Observing the Leaf :
The leaf consists of a lower sheath, which surrounds the stem or crown above the node from which it originates. There are four very important features located where the leaf blade and the leaf sheath join. The most commonly visible feature in this region is called a ligule. If present, it will appear a small piece of membranous (nearly clear cells) tissue or other appendages like hairs that project upward. These ligule characteristics are important identifying characteristics. The next key feature to look for are auricles, ear-like appendages that if present will clearly project from either side of the collar. Like the ligule, auricles will either be absent, barely visible, termed “rudimentary”, or very prominent, termed “claw-like”. The third feature to study is called, the collar, a thickened zone of yellow-green colored tissue located on the backside of the leaf where the blade and sheath join. Of the three identifying features, the collar is one of the most variable and least reliable identifying characteristics. The last feature is called the sheath, located between the crown of the grass plant and blade. The sheath may be split-open, split, with overlapping margins or completely closed.
The Leaf Tip:
The appearance of the leaf blade itself holds many clues as to which turfgrass you may be identifying. The leaf tip and upper and lower leaf surfaces can also be very helpful. Leaf tips may be pointed, rounded or boat-shaped. On the back side of the leaf blade a mid-rib may be present and the leaf blade may be glossy or shiny or dull.
The Seedhead:
Since most turfgrasses do not produce seedheads throughout much of the year and regular mowing removes seedheads this characteristic is not normally used for identification. Should the seedhead be present it will normally appear as a raceme, spike or panicle. Like with the leaf-tip, the seedhead may help narrow a grass down to certain families
Growth Habits:
One of the last features growth habit, requires a relatively mature turfgrass to determine. Turfgrasses will either be bunch-type or spreading. Spreading grasses have lateral creeping stems that if above-ground, called stolons or underground, called rhizomes.