Parts of a Grass Plant: A Glossary

How well do you know your grass anatomy? You can probably identify a blade, a root, and maybe even an awn (ouch!), but how about a culm, a rachilla, or a panicle?

Below are some of the grass-related words that you probably don’t use in everyday conversation:

Auricle: An earlike appendage at the junction of the blade and the sheath, not present in many species.
Axil: An angle formed between any two plant parts, but particularly between the culm and the upper surface of the leaf.
Collar: The outer surface of the leaf at the point where the sheath and blade join.
Corm: A short, swollen, bulblike stem that grows vertically underground. The corm stores nutrition in case of adverse conditions such as winter or drought.
Crown: The growing point near the base of the grass plant, where the shoot system joins the root system.
Culm: The stem.
Decumbent: Lying flat on the ground with the tip turned upward.
Dioecious: A species in which male (staminate) and female (pistillate) flowers are found on separate plants.
Endophyte: A plant, such as a fungus, living within the cells of another plant.
Floret: The flowering, seed-bearing part of a grass plant, located on the rachilla just above the glumes.
Glabrous: Hairless.
Glumes: The lowermost bracts or scales on the rachilla; the glumes contain no reproductive parts and serve a protective role.
Inflorescence: The flowering part of the plant; on grasses, this is what we commonly think of as the seed head.
Internodes: The part of the culm between two nodes.
Lemma: The lowermost of the two chaff-like bracts enclosing the floret. In some species, the lemma bears the pointed appendage known as the awn.
Ligule: A thin membrane or row of hairs inside the leaf blade where it joins the sheath. The ligule prevents water from running into the sheath.
Meristem: The area of cell division and growth. On a grass plant, this area is located at the junction of the leaf blade with the sheath.
Monecious: A species in which male (staminate) and female (pistillate) flowers are found on the same plant, but in different locations.
Node: A joint along the culm; leaves can grow at nodes.
Palea: The uppermost of the two chaff-like bracts enclosing the floret.
Panicle: An open, branching inflorescence with the lower branches longer than the upper ones and the flowers on stalks.
Pedicel: The stem supporting the spikelet.
Peduncle: The stem supporting the inflorescence.
Perfect: Of a flower, having both functional stamens and pistils.
Pubescence: A coating of hairs.
Raceme: A type of unbranched inflorescence in which the spikelets are connected to the stem by pedicels.
Rachilla: The central axis of a spikelet.
Rachis: The central axis of an inflorescence.
Rhizome: A runner or stem growing horizontally below the ground; a rhizome can produce new leaves and roots at nodes.
Sessile: Directly attached, versus on a stalk.
Sheath: The lower portion of a grass leaf; the part that wraps around the culm.
Spike: An unbranched inflorescence with stalkless flowers.
Spikelet: The unit that makes up the inflorescence, consisting of two glumes and one or more florets.
Stolon: A runner or stem growing horizontally along the surface of the ground; a stolon can produce new leaves and roots at nodes.
Tiller: A shoot. Tiller can also be used as a verb to describe the production of such shoots.