University of Minnesota Extension
www.extension.umn.edu
612-624-1222
Menu Menu

Extension > Agriculture > Crops > Weed management > Weed seedling identification

Weed seedling identification

O. E. Strand, former Extension agronomist
G. R. Miller, Extension agronomist

Most weed identification manuals feature mature weeds and use flower and fruit characteristics as an aid in identification. However, the grower of crops must control weeds when they are small, before they flower, to prevent them from seriously competing with crops for nutrients and soil moisture. Also, accurate identification of these seedling weeds often is necessary to select the best herbicide or other method of weed control.

New weed growth may originate either from seeds or from vegetative reproductive structures (rhizomes, rootstocks, stolons or runners, tubers, corms, or bulbs) of a perennial plant. True seedlings are those young plants that grow from seed and may include the annuals, which live for only one year, producing flowers and fruits that year; the biennials, which produce flowers and fruits the second year and then die; and the perennials, which usually produce flowers and fruits each year but continue to live for several years.

Weed seedlings also may be divided into grasses or grass-like plants and broadleaf plants.

Grass weeds

Any or all of these vegetative characteristics may be useful to help identify a young grass weed:

vegetative-grass-parts

Figure 1. Vegetative grass parts

Broadleaf weeds

All of these characteristics help in identification of broadleaf weed seedlings:

Characteristics of common grass weed seedlings

Some common grass weed seedlings with their identifying vegetative characteristics follow:

Wild Oat

wild-oat
Leaf blade rolled in round bud shoot; smooth; usually hairless, except ciliate (stiff, bristle-like hairs) often appear along lower edges
Leaf sheath often pubescent (finely and densely hairy); open, with overlapping margins
Collar broad; smooth
Auricles absent
Ligule membranous; prominent; acute
Growth habit annual

Green Foxtail

green-foxtail
Leaf blade rolled in round bud shoot; smooth; finely veined
Leaf sheath hairy; open, with overlapping margins and ciliate (stiff, bristle-like hairs) on outer margins
Collar continuous (not divided by midvein)
Auricles absent
Ligule a fringe of hairs 1 to 2 cm long; fused at the base, with longer hairs at collar margin
Growth habit annual

Yellow Foxtail

yellow-foxtail
Leaf blade rolled in a flattened bud shoot; smooth except for several prominent whitish hairs near base on upper surface
Leaf sheath smooth; flattened; sharply keeled (ridged at midvein)
Collar continuous (not divided by midvein); smooth
Auricles absent
Ligule a fringe of hairs up to 1 mm long
Growth habit annual

Giant Foxtail

giant-foxtail
Leaf blade rolled in a round bud shoot; pubescent (finely and densely hairy) on upper leaf surface, scattered hairs on lower surface; distinctly but finely veined
Leaf sheath hairy; slightly flattened, keeled (ridged at mid-vein); open with ciliate (stiff, bristle-like hairs) on margins
Collar continuous (not divided by midvein)
Auricles absent
Ligule a fringe of hairs 1 to 2 mm long; fused at the base; longer hairs at collar margin
Growth habit annual

Crabgrass, large

crabgrass-large
Leaf blade rolled in a round bud shoot; hairy on both surfaces; keeled (ridged) below
Leaf sheath very hairy; open
Collar broad; divided by midvein; hairy on outside edges
Auricles absent
Ligule membranous; prominent; rounded to acute (tapering to a point); slightly undulate (wavy-edged) on margin
Growth habit annual

Barnyardgrass

barnyardgrass
Leaf blade rolled in a flattened bud shoot; smooth; keeled (ridged) below
Leaf sheath smooth; flattened; keeled; open
Collar broad; continuous (not divided by midvein); yellowish-green; smooth
Auricles absent
Ligule absent
Growth habit annual

Quackgrass

quackgrass
Leaf blade rolled in a round bud shoot; rough on upper surface; may be somewhat hairy
Leaf sheath round; open with overlapping margins; usually pubescent (finely and densely hairy)
Collar distinct; divided by midvein
Auricles present; claw-like; slender
Ligule membranous; short
Growth habit perennial from whitish rhizomes (underground horizontal stems from which new plants can arise)

Characteristics of common broadleaf weed seedlings

Some common broadleaf weed seedlings with their identifying vegetative characteristics follow:

Velvetleaf

velvetleaf
Cotyledons spread about 32 mm; short; ovate, with long petioles; prominent and branched midvein; velvety-green
Leaves alternate; ovate, with serrated margins and long petioles; branched midvein; leaves and petioles velvety-hairy
Hypocotyl velvety-hairy
Growth habit annual

Cocklebur

cocklebur
Cotyledons spread up to 80 mm; tend to be triple veined at base; long; narrow; acute (tapering to a point) at tip; sessile (no petiole); rough
Leaves opposite, becoming alternate; triple veined at base; veins prominent; rough-hairy; short petioled
Hypocotyl rough; purplish
Growth habit annual

Field bindweed

field-bindweed
Cotyledons spread about 40 mm; broadly heart shaped; venation distinct; long petioled
Leaves dark green; shiny; glabrous; the first leaves heart shaped, margin indented at the petiole; later leaves sagittate (arrowhead shaped)
Hypocotyl smooth; often purplish; stem twining
Growth habit perennial

Canada thistle

canada-thistle
Cotyledons spread about 15 mm; oval; rough; distinctly veined
Leaves ovate; sessile (no petiole), with sharp spines and prominent midvein, becoming irregularly lobed
Hypocotyl short; whitish-green; rough
Growth habit perennial

Perennial sowthistle

perennial-sowthistle
Cotyledons spread about 20 mm; short petioled; obovate (widest near tip); smooth
Leaves first leaves smooth, shiny green, ovate, narrowed at base into a winged petiole; later leaves variously lobed or toothed; teeth reflexed (bent backward); weak spined; milky juice
Hypocotyl short; smooth; stem with milky juice
Growth habit perennial

Wild mustard

wild-mustard
Cotyledons spread about 26 mm; wider than long, with shallow oval notch or indentation at tip; long glabrous petioles; branched midvein
Leaves alternate; oval to spatulate (spoon shaped) with undulate (wavy-edged) or bluntly toothed margins; prominent and branched midvein; trichomatous (with hairlike projections) on leaves and petioles
Hypocotyl usually reddish in color
Growth habit annual

Kochia

kochia
Cotyledons spread about 11 mm; linear shape with no petioles (sessile); sometimes faintly veined; gray or frosty-green on upper surface and red on lower; circular swelling at growing point between cotyledons
Leaves appear opposite but become alternate--pairs are so close together they form a small rosette between cotyledons; linear shape with no petioles; very hairy
Hypocotyl reddish to purplish in color
Growth habit annual

Russian thistle

russian-thistle
Cotyledons spread about 25 mm; extremely long, narrow shape, with no petioles
Leaves opposite, becoming alternate; extremely long, narrow, threadlike shape, with no petioles; older leaves barb tipped
Hypocotyl reddish in color
Growth habit annual

Common lamb's-quarters

common-lambs-quarter
Cotyledons spread about 13 mm; linear shape; red on lower surface, light green on upper
Leaves opposite, becoming alternate; oval to ovate; light green with frosty or white mealy appearance; short petioles; mid-vein with little or no evident branching
Hypocotyl light red in color
Growth habit annual

Redroot pigweed (Prostrate pigweed and Hybrid pigweed are very similar)

redroot-pigweed
Cotyledons spread about 14 mm; linear shape, with short petioles; lower surface and midvein on upper surface reddish in color
Leaves alternate; ovate to oval, with indented tips and medium-long, sparsely trichomatous (with hairlike projections) petioles; branched midvein
Hypocotyl light red in color
Growth habit annual

Wild buckwheat

wild-buckwheat
Cotyledons spread about 25 mm; linear shape, with short petioles; prominent midvein on lower surface and sometimes on upper
Leaves alternate; ovate, with long, pointed tip giving a heart shaped appearance; long petioles; prominent and branched midvein; each bears an ochrea (membranous sheath) at base of petiole; small trichomes (hairlike projections) on stem and leaf petiole
Hypocotyl short; reddish; often covered with short, bristle-like projections
Growth habit annual

Pennsylvania smartweed

pennsylvania-smartweed
Cotyledons spread about 41 mm; linear on one edge, curved on the other; reddish blotch on lower surface; sparsely trichomatous (with hairlike projections) on margins
Leaves alternate; long oval to spatulate (spoon shaped); prominent midvein; each leaf bears an ochrea (membranous sheath) at base of leaf petiole; sparsely trichomatous (with bristly hairs) on margins
Hypocotyl reddish in color; smooth
Growth habit annual

Common ragweed

common-ragweed
Cotyledons spread about 21 mm; broadly spatulate (spoon shaped) to short oval, with broad petioles; veined at base on lower surface, not veined to faintly veined on upper surface; thick and waxy, with dark spots on margin of lower surface and sometimes on upper surface
Leaves opposite; five lobed, with terminal lobe sometimes toothed; branched midvein; long petioles; leaves and petioles densely hairy
Hypocotyl purple to dark green in color
Growth habit annual

Giant ragweed (Kinghead)

giant-ragweed
Cotyledons spread about 50 mm; broadly spatulate (spoon shaped) to oval, with broad petioles; triple veined at base on lower surface; midvein only on upper surface; thick and waxy; spotted on margin of lower surface
Leaves opposite; three lobed, with terminal lobes toothed; branched midvein; petioles and leaves short, hairy
Hypocotyl purple in color
Growth habit annual

Marshelder

marshelder
Cotyledons spread about 11 mm; short oval, with broad petioles and blunt tips
Leaves opposite; narrowly ovate, with pointed tips; branched midvein; leaves and petioles densely and coarsely hairy
Hypocotyl often turns reddish
Growth habit annual

White cockle

white-cockle
Cotyledons spread about 22 mm; ovate
Leaves opposite; oval to spatulate (spoon shaped) with pointed tips; midvein on lower surface, absent or faint on upper surface; leaves and petioles densely hairy, greenish-gray
Hypocotyl short; greenish-gray; hairy
Growth habit biennial or short-lived perennial

Pennycress

pennycress
Cotyledons spread about 19 mm; short oval, with long and slender petioles
Leaves first leaves appear opposite, later alternate, several appearing together to form a rosette; short ovate to short oval, with toothed margins and long petioles; lightly branched midvein; garlic-like odor when crushed
Hypocotyl short; smooth
Growth habit annual or winter annual

Shepherd's-purse

shepherd's purse
Cotyledons spread about 10 mm; oval to ovate, with medium-long petioles; midvein none to faint on lower surface
Leaves first leaves appear opposite, later alternate, becoming a rosette; oval to ovate; midvein on lower surface; hairy
Hypocotyl short
Growth habit annual or winter annual


Copyright © 2013 Regents of the University of Minnesota. All rights reserved.
WW-00776 Reviewed 1999

  • © 2014 Regents of the University of Minnesota. All rights reserved.
  • The University of Minnesota is an equal opportunity educator and employer. Privacy