Plant Identification

Introduction to Weed Identification

Identifying plants is essential to get access to what other people have learned. Here are some of the features of plants that distinguish one from another and a glossary of the common terms used to label the features. Since some distinguishing features of plant flowers are quite small, you will need a hand lens of 10x magnification or a smart phone magnifier. My phone’s camera provides 8x magnification, but that’s not quite enough. The glossary follows the illustrations.

Weed Anatomy Images

Grass spikelet. Artist unknown (link broken).



Weed Anatomy Glossary

A following list includes general terms used in the text. Definitions are from several sources; most are from Parker (1972).

  • Achene:  A small dry one-seeded fruit in which the ovary wall is free from the seed
  • Anther:  Enlarged part at the top of the stamen; bears the pollen
  • Awn:  A bristle or spine, as at the tip of some bracts of grasses
  • Axil:  The upper angle between the stem and the leaf
  • Bract:  A modified leaf underneath a flower or inflorescence
  • Bur:  A rough or prickly envelope around a seed or fruit
  • Calyx:  The outer set of floral leaves, usually green, composed of all the sepals
  • Corolla:  The set of floral leaves, usually showy, composed of all the petals
  • Deciduous:  Dropping off; shedding of leaves at the end of the growing season
  • Dehiscent:  Splitting open at maturity
  • Disk flowers:  The tubular flowers in the center of the flower heads in the sunflower family
  • Embryo:  A young plant enclosed in a seed
  • Entity:  Natural vegetation unit defined by plant species presence
  • Floret:  A small flower in the spikelet of the grasses, or the flower head of the sunflower family
  • Flower head:  A dense inflorescence of stalkless flowers
  • Frond:  The leaf of a fern
  • Fruit:  The seed case or seed pod (the ripened ovary); containing anywhere from one to many seeds
  • Glands:  Secreting tissue
  • Glumes:  A pair of bracts at the base of the grass spikelet
  • Grain:  The seed-like dispersal unit of the grass family
  • Inferior ovary:  Where the sepals, petals, and stamens appear to rise from the very top of the ovary
  • Inflorescence:  Flowers on a stalk, as a spike, raceme, head, panicle
  • Involucre:  A cluster of bracts
  • Keel:  A central dorsal ridge; the two united petals in some legume flowers
  • Leaflet:  A division of a compound leaf
  • Mycorrhiza:  Formed by a combination of underground threads and rootless
  • Node:  That position on the stem where a leaf, leaves, or branch arises
  • Nutlet:  A small nut; the one-seeded part of a larger fruit that separates at maturity
  • Ovary:  Base of the female part of the flower (pistil); ripens into the fruit
  • Panicle:  A loose, irregularly branched inflorescence with stalked flowers
  • Pappus:  The modified calyx of a disk or rayflower in the sunflower family
  • PAR:  BLM’s pesticide application record
  • Petaloid:  Petallike
  • Ray flower:  Marginal petallike flowers in the inflorescence of the sunflower family
  • Relevés:  Representative vegetation observation
  • Rhizome:  A horizontal underground stem
  • Rosette:  A cluster of spreading or radiating basal leaves
  • Runner:  A horizontal aboveground stem; a stolon
  • Sepal:  One of the outer set of floral leaves or calyx, usually green
  • Sheath:  The basal portion of the leaf which clasps the stem
  • Spike:  An unbranched inflorescence where the flowers are not stalked
  • Spikelet:  The unit of the inflorescence in grasses
  • Stamen:  The male part of the flower
  • Stipule:  One of a pair of appendages at the base of the leaf
  • Stolon:  A horizontal, underground stem
  • Succulent:  Soft and fleshy in texture
  • Tuber:  A swollen underground stem
  • Volva:  The membranous envelope enclosing an immature mushroom
  • Whorl:  Three or more leaves or flowers arising from the same node