Weed ID and Biology

  • Common chickweed
    Common chickweed (Stellaria media)
  • Texas panicum
    Texas Panicum (Urochloa texana)
  • Saltgrass
    Saltgrass (Distichlis spicata)
  • Yellow nutsedge
    Yellow Nutsedge (Cyperus esculentus)

*Photo credits

Weed Types

Broadleaf Weeds

Describes a generalized group of weeds whose growing point is above ground.

Grasses

A large, hardy family of plants whose growing point is below ground.

Sedges

Family of plants closely related to grasses with the distinguishing characteristic of having a triangular cross-sectioned stem.

*The lists of weeds provided are not exhaustive

Botany Terminology for Weed Identification

Life Cycle

Annual- grows, reproduces, & dies back within one growing season

          - Summer annuals germinate during warm seasons

          - Winter annuals germinate during cool/cold seasons

Biennial- grows, reproduces, & dies over a two-year period

Perennial- live & reproduce indefinitely, may have periods of dormancy

Roots

Root Type Root Type Description Root Type Image
Taproot Long central root w/ smaller secondary roots extending out taproot
Fibrous roots Many long, branching roots w/ smaller secondary roots extending out fibrous roots
Adventitious Roots formed from areas of the plant other than the root meristem, generally from the stem adventitious roots

Perennial Growth Structures

Perennial Growth Structure Type Perennial Growth Structure Description Perennial Growth Structure Images
Rhizome

Horizontal stem that forms beneath the ground & sends up shoots above ground & roots below ground

rhizome

Tuber

Large carbohydrate-rich storage organ that forms beneath the ground

tubers

Stolon

Horizontal stem that extends runners above ground that produce new plants w/ complete shoots and roots which produce more runners

stolon

Bulb

Large storage organ that forms beneath the ground comprised of a small stem surrounded by layers of fleshy storage leaves

 

bulb

Leaf Shape Types

Elliptic Lanceolate Linear
Elliptic leaf Lanceolate leaf Linear leaf
Oblong Obovate Orbicular
Oblong leaf Obovate leaf Orbicular leaf
Ovate Reniform Spatulate
Obovate leaf Reniform leaf Spatulate leaf

Leaf Arrangements

Leaf Arrangement Type Leaf Arrangement Description Leaf Arrangement Image
Alternate

Leaves grow on a single side of the stem per node

alternate leaves

Opposite

Leaves grow on both sides of the stem per node

opposite leaves

Basal rosette

A ring of leaves that forms around the base of the stem                                

basal rosette

Whorled

A ring of leaves that forms along the stem

 

whorled leaves

Leaf Margins

Leaf Margin Type Leaf Margin Description Leaf Margin Image
Entire

Round leaf margin                                                                                                                   

entire margin

Crenate

Crinkled leaf margin

crenate margin

Serrate

Saw-like leaf margin

serrate margin

Palmate

Leaflets coming off the end of a single leaf petiole

palmate margin

Pinnate

Leaflets branching out along the length of a single leaf petiole

pinnate margin

Growing Habits

Growing Habit Type Growing Habit Description Growing Habit Image
Erect

Stem growing straight up                                       

erect stem

Climbing via tendrils

Stem grows up along a surface using tendrils                                      

climbing tendrils

Climbing via twining

Stem grows up a surface by wrapping around it

climbing twining

Ascending

Stems growing up & out

ascending

Decumbent

Stems growing out horizontally but curve up at the ends

decumbent

Prostrate

Stems growing out horizontally along the ground

prostrate

Grass Identification Tips

Because the leaves and flowers of grasses can often look similar to one another, being able to identify the unique anatomical features that can be used to differentiate between the various grass genera and species is important. 

Grass Features
Grass Feature Name Grass Feature Description Grass Feature Image
Awn

A spike or bristle extending off grass seeds found in some grass species

awn

Blade

Leaf of a grass plant

blade

Pubescent

Covered in hairs

hair

Glabrous

Completely lacking hairs

no hair

Sheath

Area at base of leaf that wraps around the stem of grass plant

sheath

Ligule

Membrane or fringe of hairs near the area where the leaf sheath & blade meet (called the collar)

membranous

hairy

Auricle

Extension at base of leaf blade present in some grass species; adjacent to collar between blade and sheath

auricle

Panicle inflorescence

Type of flower where flower clusters are attached to stem by branchlets connected to branches coming off the stem

panicle

Raceme inflorescence

Type of flower where flower clusters are attached to stem by branches connected to the stem

raceme

Spike inflorescence

Type of flower where flower clusters are attached directly to stem

spike

ReferencesWeeds of the South by Charles T. Bryson and Michael S. DeFelice, Weeds of the Northeast by Richard H. Uva, Joseph C. Neal, and Joseph M. DiTomaso
Leaf shape diagrams: Wikimedia