Noxious Weeds Glossary

Alternate – Leaves that are arranged singly up the stem; not opposite each other.

Annual – Plant that germinates, flowers, seeds, and dies during one growing season.

Anther – Structure in a flower in which pollen is formed

Auricle – Lobe-like structure at the collar of a grass leaf.

Awn – Slender bristle at the tip of grass seed structures.

Axil – The angle formed between a leaf and a stem.

Basal – At the base of a plant or plant part.

Biennial – Plant that germinates in one growing season, then flowers, seeds, and dies during a second.

Bract – Leaf like structure at the base of flowers or leaves.

Calyx – All the flower leaves together, normally green in color.

Clasping leaves – Leaves that appear to wrap around the stem at their base.

Compound Leaves – Leaves with 2 or more distinct leaflets.

Cotyledons – The first leaf-like structures that appear after germination; seed leaves.

Crown – The structure formed where leaves, stems, and roots grow together.

Dissected – Deeply and repeatedly divided into smaller parts.

Entire – Not toothed or otherwise cut.

Glumes – The 2 bracts surrounding a grass spikelet.

Head – A group of flowers borne tightly together.

Leaflets – Leaf-like structures within a compound leaf.

Ligule – The structure at the collar of a grass leaf between the sheath and the stem.

Linear – Long, narrow, and slender.

Lobed – A cut into a leaf from the edge toward the center; greater than toothed, but not quite compound.

Margin – The edge of a leaf.

Membranous – Thin and flexible, usually not green.

Midrib – The center and usually most prominent vein on a leaf.

Nodding – A flower that is not pointed upward, but bent downward or sidewise to the stem.

Opposite – Leaves situated directly across the stem from each other.

Ovate – Egg shaped in outline.

Panicle – A much-branched inflorescence.

Perennial – A plant that lives for more than 2 growing seasons.

Petiole – A leaf stalk.

Pinnate – With 2 rows of leaflets, like a feather.

Plume – A hair-like or feather-like structure, often on a seed.

Pubescence – The hairs on a leaf, stem or flower.

Rhizome – A creeping, underground stem.

Rosette – A circular, normally basal, clump of leaves.

Sheath – The extension of leaf tissue surrounding a stem.

Simple leaf – One with a blade in one piece; not compound.

Spike – A narrow, non-spreading inflorescence.

Spikelet – A single or group of floral structures in a grass.

Spur – A hollow appendage on a flower.

Stolon – A creeping stem along the surface of the ground.

Succulent – Fleshy and juicy.

Taproot – A thick, central root with minimal branching.

Trifoliate leaf – A leaf made of 3 leaflets; clover-like.

Whorled – 3 or more similar structured arranged as spokes on a wheel.


© 1999 University of Idaho: Text and photographs for these pages from Idaho’s Noxious Weeds, by Robert H. Callihan and Timothy W. Miller (revised by Don W. Morishita and Larry W. Lass).

Please contact: Ag Publishing, University of Idaho, Moscow, Idaho 83844-2240; (208) 882-7982; [email protected]; or visit the UI Extension/CALS Publications and Multimedia Catalog website at, for more information about this or other publications.