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; ; or visit the Resources for Idaho website at , for more information about this or other publications.