Grass-like plants can be difficult to identify because the main traits we use for identifying broadleaf plants – leaf shape and flowers – don’t vary as much between these species. To identify grass-like plants (grasses, sedges, and rushes), it helps to know which traits to look for This diagram shows a grass plant with the traits commonly used for grass identification labeled.
From the roots up: Stolon, fibrous roots, rhizome, crown, tiller, node, sheath, leaf blade (includes midrib), sheath, collar region (includes ligule and auricle), and inflorescence.
Illustration by Isabella Colucci
Leaf bud
One of the first characteristics to consider when identifying grass-like plants is the shape of the leaf bud. In the field this can be determined by rolling the plant back and forth between your fingers. If the specimen is only able to flip from one side to the other then it is a folded leaf bud. If it is able to roll smoothly, it is a rolled leaf bud. Folded vs rolled can also be observed by looking at the cross sections of the stem; the difference is shown in the cross section diagram.
If the specimen has three edges (triangular) then it is a sedge species. A trick to remembering the general name for species with triangular stems is the saying “sedges have edges.” New York State has many sedge and flat sedge species (264 species in total*), but since only one species, yellow nutsedge (Cyperus esculentus) is a major weed for agricultural landscapes, this page will mainly discuss ID characteristics specific to grasses. For more specific information on sedges, visit the New York Natural Heritage Program’s plant guides homepage and explore their sedge species pages.
*Number derived from New York Flora Atlas by adding together Carex species and Cyperus species.
Three leaf buds of grass-like plants with their cross sections. From left to right: folded, rolled, then triangular.
Illustration by Isabella Colucci
General characteristics of grass plants (from the ground up)
The root system:
Fibrous roots consist of finely branching roots originating from another root or the stem.
Stolons (also called runners) are a form of vegetative reproduction, and are modified horizontal stems that extend above ground and form a new plant at its tip or axillary buds.
Rhizomes are also a form of vegetative reproduction, and are a modified stem that roots below ground.
Tillers are aboveground shoots that grow from the base of a stem.
Close up of root system, featuring fibrous roots, stolons, rhizomes, and tillers.
Illustration by Isabella Colucci
Above ground:
The crown is the tissue that attaches the roots to the shoot.
Nodes are where leaves are (or previously have been) attached to the stem. In some grass species, nodes have the ability to root and can therefore vegetatively spread.
The sheath is the lower part of the leaf that surrounds the stem and budding leaves.
The leaf blade is the part of the leaf that extends out from the stem, above the collar region. Leaf blade length, width, and hairiness on the top/bottom/edges of the leaf blade are all good traits to look for on a grass leaf.
Grass-like plant characteristics featuring leaf blade, sheath, node, and crown.
Illustration by Isabella Colucci
The leaf blade also has what’s called a midrib, the middle vein on the blade. This characteristic can be quite distinctive depending on the species you are looking at, which can help in identifying your grass specimen. The illustration on the right locates this characteristic on the leaf blade.
Features midrib in highlighter yellow with the collar region, stem, and sheath identified to help with orientation.
Illustration by Isabella Colucci
The collar region also comes in various forms as shown by the illustration on the right. The collar is where the blade joins the sheath.
Two different collar region categories shown in highlighter yellow. The one on the left is divided and the one on the right is continuous. Each can be broad or narrow depending on the species.
Illustration by Isabella Colucci
The collar region also includes the characteristics, ligules and auricles. Differences between these characteristics are highlighted in yellow.
The ligules and auricles are (if present) are where the sheath and blade meet. The ligule can either be absent, membranous, or a fringe of hairs. The auricles may be absent, short/blunt, or long/clasping. Understanding the differences between each of these characteristics can greatly inform your identification of a particular species.
Top row (from left to right) are the ligule classifications: absent, membranous, and fringe of hairs. Bottom row (from left to right) are the auricle classifications: absent, short, and clasping.
Illustration by Isabella Colucci
The inflorescence (a group of flowers) can have multiple morphological forms. These are commonly the panicles, spikes, and racemes forms in grass species.
A panicle has a central axis with branches. It can appear open or compact (spike-like).
A spike is unbranched and the spikelets* lack a stalk between them and the central stalk of the flower head.
A raceme is a lengthened flower head with an unbranched central stalk.
*spikelet may contain one to many individual flowers and has tiny specialized leaves.
Three flower head examples of grass inflorescence. Top left: open panicle; Top middle: Long spike; Bottom right: one-sided raceme.