Grass Plant Identification

Flower heads on grass

Thanks to their contribution to agriculture and society as a whole, the grass family (Poaceae) remains one of the most important plant families. Grass plants resemble sedges and rushes, but maintain their own characteristics. The best time for grass plant identification comes when the grass specimen you wish to identify blooms. However, while grasses do not always bloom, other characteristics exits to guide the identifier to the correct grass species.

Poaceae

The name "Poaceae" encompasses the entire grass family, providing the umbrella for 700 genera of grasses. As one of the largest families of plants, Poaceae contains more than 10,000 species of grass plants, writes Washington State University Extension. In North America, 1400 of those species grow both in the wild and cultivated in gardens, yards and fields.

Defining Characteristics

According to the Mount Vernon Research Center at Washington State University, grass plants maintain 3 defining characteristics from other members of the plant kingdom. First, petal-less flowers emerge between the bracts on leaf-less stems. Next, the leaves on grass plants take on a flat form and stretch out long and slender. At the stem, these leaves cling tightly and form a type of sheath. Finally, the round stems remain hollow in the center. The nodes, or joints, along the stem also appear swollen.

Monocotyledons

A grass's monocotyledons status distinguishes it from most every other flower plant. Poaceae actually belongs to a further subdivision of monocotyledon, Gramineae. Recognizing the Gramineae trait provides the perfect first step for identifying grass plants. Gramineae, according to the Offwell Woodland and Wildlife Trust, bears inconspicuous flowers, lacking in petals, on spikes and have papery scales, called chaff. The fruit itself contains only one seed. The flower head unit as a whole goes by the name of spikelet.

Flower Head

The flower heads, or inflorescence, take on one of three forms, which provides an opportunity to distinguish between specific grass species. Flower heads called panicles teeter on top of stalks that branch out from the main stem. If the main stems grow on stalks that do not branch out, they get labeled raceme. A flower head sans both branching and stalks grow merely as a spike, since the flower head rests on the spikelet itself.

Grass Structure

Another way for grass plant identification lies in distinguishing structure. While all grass stems grow hollow in the center and produce swollen nodes, the way they grow distinguishes one grass from another. Some grasses, stolons, creep horizontally along the ground, sending up new shoots at the nodes. A few grass plants, culms, branch vertically. The structure of the leaf blade, along with growing long and flat, usually taper to a point or blunt tip.

References

• WSU Mount Vernon Research Center: Puzzled by Poaceae?--A Grass Identification Workshop
• Offwell Woodland & Wildlife Trust: Grass Identification

Resources

• Wayne's Word Palomar College: Grass Family (Gramineae or Poaceae)