Glossary of Weed Terms

Aerial: Occurring above ground or water.

Alternate: Leaf attachments are singular at nodes, and leaves alternate direction, to a greater or lesser degree, along the stem.

Annual: An annual plant is a plant that usually germinates flowers and dies in one year.

Auricles: Earlike structures found at the junction of the blade and sheath; extensions of the leaf blade around the stem.

Awn: A narrow, hair-like bristle

Axil: The position between the stem and a leaf.

Axillary: Positioned in or arising in an axil.

Basal rosette: Cluster of leaves radiating form the base of the stem at ground level.

Bract: A reduces leaf or leaf-like structure at the base of a flower or flower cluster.

Bristle: A short, stiff hair or hair-like structure.

Collar: The area on the outside of a grass leaf at the junction of the blade and the sheath.

Cotyledon: A primary leaf of the embryo; a seed leaf.

Creeping roots: Thickened roots that store carbohydrates, spread vertically and horizontally in the soil, and contain adventitious buds that give rise to new plants.

Disk flower: The central flowers of a flower head in the Asteraceae (aster family).

Disseminate: To disperse throughout.

Glume: One of the paired bracts at the base of a grass spikelet.

Herbaceous: A non-woody plant with stems and leaves that die back to the ground in the winter.

Ligule: A membraneous or hairy structure arising on the inside of the leaf at the junction of the blade and sheath.

Node: The position on the stem where leaves or branches originate.

Ocrea: A membranous, papery sheath around the stem at the nodes as in members of the Polygonaceae (smartweed family).

Palmate: Lobed, veined or divided from a common point, like the fingers of a hand.

Panicle: A flower cluster with a main axis and subdivided branches that is often pyramid-shaped.

Pappus: The feathery or hairy portion of a seed used to facilitate wind dispersal.

Petiole: A leaf stalk.

Pinnate: The word used to describe a compound leaf with leaflets arranged on opposite sides of an elongated axis.

Prickle: A small, sharp outgrowth of the stem surface.

Ray flower: The strap-like outer flowers of a flower head in the Asteraceae (aster family).

Rhizome: Belowground modified stem that gives rise to new plants.

Samara: A dry, winged fruit.

Sepal: The outermost part of a flower; typically green and leaf-like.

Spikelet: The individual flower clusters of grasses and sedges, consisting of one to many flowers subtended by two bracts (glumes).

Spine: A stiff, slender, sharp-pointed structure arising from below the epidermis.

Stipules: A pair of leaf-like structures found at the base of a leaf.

Stolon: Aboveground modified stem that gives rise to new plants.

Summer Annual: Summer annuals sprout, flower and die within the same spring/summer/fall.

Terminal: The tip or end of a stem or leaf.

Thorn: A stiff, woody, modified stem with a sharp point.

Tiller: A shoot, especially one that sprouts from the base of a grass.

Trifoliolate: The word used to describe a compound leaf consisting of three leaflets.

Tuber: The thickened portion of a rhizome bearing nodes and buds; underground stem modified for food storage.

Whorl: Arrangement of three or more parts arising from a common point, as in a leaf arrangement with three or more leaves per node.