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Michael A. Schnelle
Extension Horticulture Specialist
There are several features that can be used to distinguish grassy turfgrass weeds (Figure 7-1). Vernation is the arrangement of a leaf or leaves in the bud shoot. They may be classified as rolled or folded. The tubular portion of the leaf which wraps around or encloses the stem is the sheath. Edges of the sheath may join, overlap, or be closed. The sheath may also be rough or smooth, cylindrical, flattened, or compressed. Ligules clasp the stem at the junction of the leaf blade and sheath. The type (membranous or hairy) and shape (tall, short, or jagged) remain fairly uniform and constant within each given species. The collar is the area on the outer side of the leaf where the blade and the sheath join. It is generally much lighter in color and varies in size and shape from species to species. Auricles are found on either side of the collar and may be clawlike, long, or short. Rhizomes are underground stems that can produce new plants, while stolons are above ground stems capable of producing new plants. The seedhead or inflorescence is the collection of flowering parts which are arranged invarious ways (i.e., spike, panicle, etc.). Spikelets are small units of the seedhead which contains the seed parts.
Winter Annual Grassy Weeds
Annual Bluegrass (Poe annua)
Other names: Wintergrass, Poa, and speargrass.
Growth habit: This grassy weed is capable of growing at mowing heights lower than one-fourth inch. It thrives
in cool, moist weather or damp, shaded locations. It is apple green in color and produces hundreds of whitish green
seedheads at any mowing height. Blades are weak and terminate with a boat-shaped tip. In hot weather, annual bluegrass
dies, leaving unsightly dead patches in an otherwise green lawn.
Leaf blade: Folded in the bud, soft, glossy, light green with boat-shaped tips, one-eighth inch wide and
often wrinkled.
Sheath: Slightly compressed, smooth.
Ligule: Medium long, pointed, white, membranous.
Auricles: None.
Collar: Narrow, smooth, and continuous.
Seedhead: Short, branching, open, and greenish white.
Spikelets: Flattened, with three to six florets.
Summer Annual Grassy Weeds
Crabgrass (Digitaria spp.)
Other names: Large crabgrass, hairy crabgrass, smooth crabgrass.
Growth habit: This pale green annual has short, sparse hair with blades that taper to a point. Fingerlike
seedheads producethousands of seeds which germinate in the spring when soil temperatures reach 55°F.
Leaf blade: Rolled in the bud, sparsely hairy or smooth, about one-fourth inch wide, tapers to sharp point.
Sheath: Compressed and smooth or hairy.
Ligule: Long, acute, membranous, toothed margin.
Auricles: None.
Collar: Broad and sparsely hairy.
Seedhead: Three to 13 narrow racemes at the top of the stem.
Spikelets: Found in two rows, elliptical, sparsely hairy.
Yellow and Green Foxtail (Setaria spp.)
Other names: Wild millet.
Growth habit: Leafy summer annual which reaches maturity in midsummer and is often confused with crabgrass
until it flowers. Texture is coarse and forms tufts in mowed turf. It usually germinates between crabgrass and
goosegrass.
Leaf blade: Rolled in the bud, flat, often having a spiral twist, hairy on the upper surface near the base,
one-fourth inch or more wide, tapering to a sharp point.
Sheath: Compressed, smooth, tinged with red.
Ligule: A fringe of short hairs.
Auricles: None.
Collar: Broad, continuous, and smooth.
Seedhead: Coarse and bushy which resembles the tail of a fox.
Spikelets: Ridged with several bristles and contains one seed.
Goosegrass (Eleusine indica)
Other names: Silver crab, hard crab, and crowfoot.
Growth habit: Goosegrass is an annual grassy weed which thrives in full sun and compacted soils. Stems,
leaf blades, and seedheads lie flat on the ground in a rosette pattern and tolerate close mowing. It germinates
later in the spring season than crabgrass.
Leaf blade: Folded in the bud, coarse texture, dark green, about one-fourth inch wide, and tapering to a
point. Blades are very tough and wiry.
Sheath: White near the ground, green above, tightly compressed, overlapping, sparsely hairy along margins.
Ligule: Medium long, membranous, toothed, deeply divided at the mid-rib.
Auricles: None.
Collar: Broad, continuous, and sparsely hairy.
Seedhead: Two to 10 narrow racemes at the top of the main stem which are much broader than crabgrass.
Spikelets: Flat and contain ridged seed.
Sandbur (Cenchrus inceratus)
Other names: Burgrass.
Growth habit: This pale green, low-growing annual is a common problem on sandy soils. It is found in dense,
spreading, patches and is extremely objectionable because of the barbed burs which easily pierce the skin.
Leaf blade: Folded in the bud, few hairs near the ligule, onefourth inch wide, tapering to a point. Upper
blades often enclose seed burs.
Sheath: Loosely compressed, margins are sparsely hairy.
Ligule: Short, even fringe of hairs.
Auricles: None.
Collar: Broad, continuous, sometimes with a few long hairs on edges.
Seedhead: Single spike with six to 20 burs.
Spikelets: Broad at the base and tapering to a point, two seeds in each bur.
Barnyardgrass (Echinochloa cruspalli)
Other names: Watergrass, panicgrass, and barngrass.
Growth habit: A coarse-textured annual with broad, compressed, purple sheaths that lie flat on the ground
and spread in a semi-circular pattern under close mowing. Usually germinates later than crabgrass.
Leaf blade: Rolled in the bud, long, tapered, heavy mid-rib, and dark green in color.
Sheath: Compressed, smooth, tinged with purple.
Ligule: None.
Auricles: None.
Collar: Broad and continuous.
Seedhead: Green to reddish purple, with conspicuous, short, stiff bristles.
Spikelets: Barbed with long or short awns.
Perennial Grassy Weeds
Bermudagrass (Cynodon dactylon)
Other names: Devilgrass.
Growth habit: An aggressive perennial grass which can be a serious weed.
Leaf blades: 3mm wide, gray-green, slightly hairy or glabrous (hairless), except for a fringe of long hairs
at the edge just above the collar.
Sheath: Two opposite per node, sparsely hairy or hairless, strongly flattened.
Ligule: A conspicuous ring of white hairs.
Seedhead: Erect or ascending.
Spikelets: In two rows tightly compressed to one side of the rachis.
Dallisgrass (Paspalum dilatatum)
Other names: Watergrass.
Growth habit: This clumpy perennial spreads by seed and vegetatively by rhizomes, and it has blades which
are nearly one-half inch wide. It is one of the first grasses to begin growth in the spring and it is difficult
to control.
Leaf blade: Rolled in the bud, about one-half inch wide, eight to 10 inches long, tapering, with a few hairs
near the ligule.
Sheath: Compressed, slightly keeled.
Ligule: Membranous, rather tall, nearly pointed.
Auricles: None.
Collar: Broad, continuous.
Seedhead: Three to six slender racemes branching off the main stem.
Spikelets: Round with pointed tips and hairy at the base.
Johnsongrass (Sorghum halepense)
Growth habit: Perennial, reproducing by large rhizomes or by seed.
Leaves: Alternate, smooth, simple, 20 to 50 cm long, less than 2 cm wide.
Panicles: Large, purplish, hairy, 15 to 50 cm long.
Spikelets: Long, ovate with flat-lying straight hairs.
Yellow Nutsedge (Cyperus esculentus)
Growth habit: Perennial herb, reproducing by seeds and threadlike stolons ended with tubers.
Leaves: Three-ranked, pale green.
Sheaths: Closed and mostly basal.
Spikelets: Yellowish to golden brown, four-ranked.
Broadleaf Weed Identification
Characters used to identify broadleaf weeds found in turfgrasses include the growth habit, leaves, stems, flowers, and seeds (Figure 7-2). Growth habit includes the time the weed is actively growing, whether it grows upright or prostrate, and climatic conditions which favor germination and growth. Leaves can be characterized by their shape, the presence of hairs, the type of margins, and whether they are opposite or alternate on the stems. Stems may be round or square, hairy or smooth, and be able to branch and root at the lower nodes. Flowers differ by their color, shape, size, and number. Flowers may be located at the primary growing point (apex) or in leaf axils (axillary). Seeds differ primarily by their size, shape, and color.
Winter Annual Broadleaf Weeds
Henbit (Lamium amplexicaule)
Other names: Dead nettle, blind nettle, bee nettle.
Growth habit: This winter annual weed grows upright and is a member of the mint family. It first appears
in late winter and dominates in early spring. Henbit is very difficult to control.
Leaves: Rounded, hairy, and deeply veined leaves have coarsely toothed margins. The leaves are opposite
on petioles in the lower portion of the stem. The upper leaves are attached or clasping the stem.
Stems: Several upright, green to purple, square stems are able to root and branch at the lower nodes.
Flowers: Whorls of irregularly shaped flowers are found in the axils of the upper leaves. Petals are purple
and fused into a trumpet-shaped tube.
Seed: Nutlets are produced which contain grayish brown, speckled seeds.
Cranesbill (Geranium carolinianum)
Other names: Carolina geranium, cutleaf geranium.
Growth habit: Freely branched annual weed which remains prostrate in turf. Fine hairs can be found on the
stems and leaves.
Leaves: Leaves are deeply dissected into five to seven lobes. Each lobe is again lobed and bluntly toothed
on the margins.
Stems: The branching stems grown along the ground and have fine hairs.
Flowers: Two to several conspicuous, small flowers are borne together on stalks from the upper nodes. It
blooms mostly in April and May. Individual flowers have five pink to lavender petals.
Seed: Seeds have a conspicuous "cranesbill" beak about one-half inch long.
Shepherdspurse (Capsella bursapastoris)
Other names: Shepherd's bag, pepper plant, case weed, pick-purse.
Growth habit: This annual weed is a member of the mustard family and often a problem in newly seeded areas.
It grows from a rosette and forms a slender taproot.
Leaves: Alternate, narrow, toothed, or lobed leaves form a rosette and are similar to dandelion. Leaves
on flower stems clasp or wrap around the stem and do not have milky sap.
Stems: If it is not mowed and is allowed to grow, erect stems produce arrow-shaped leaves.
Flowers: Tiny, white flowers with four petals bloom very early in the spring.
Seed: Heart-shaped or triangular capsules, which contain many reddish brown seeds, resemble purses worn
by shepherds in ancient Biblical times.
Mouseear Chickweed (Cerastium vulgatum)
Growth habit: This perennial weed acts as a winter annual in Oklahoma and has a vigorous prostrate growth
habit. It reproduces by seed and creeping, hairy stems which hug the ground. Mowing only stimulates a more vigorous
habit of prostrate growth.
Leaves: Sticky, hairy leaves are opposite, oblong, dark green, and rounded on the ends.
Stems: Hairy stems may creep along the ground and take root at nodes that touch the soil.
Flowers: Has small, white, inconspicuous flowers that have five slightly notched petals.
Seed: Small orange or brownish seeds are somewhat transparent with a rough seed coat.
Common Chickweed (Stellaria media)
Other names: Starweed, winterweed, satin flower, tongue grass.
Growth habit: A low-spreading winter annual with a weak, shallow root system that can cover adjacent turf
and form extensive, dense patches. Grows best during cool, wet weather in shady places and rarely tolerates hot,
dry conditions.
Leaves: Leaves are bright shiny green, opposite, smooth, oval, and tapered to a point.
Stems: Stems are slender, branched, and have a row of fine hairs on one side. The stems creep along the
ground and can root at the nodes.
Flowers: Small, white flowers are borne in clusters at the end of the stems. Flowers have five deeply notched
petals and, though small, are quite noticeable.
Seed: Numerous rough, dark brown seeds are produced which germinate from late fall through early spring.
Winter Perennial Broadleaf Weeds
Dandelion (Taraxacum officinale)
Other names: Lions-tooth, puffball, blowball.
Growth habit: This broadleaf weed is a very hardy perennial with a strong taproot which penetrates the soil
two to three feet. The above-ground rosette remains the entire year. New seedlings can appear any time during the
fall or early spring.
Leaves: Long, narrow leaves are lobed or serrated with the tips or points of these lobes usually opposite
each other and pointing back toward the center of the rosette. The leaves are often purple at the base and emit
a milky sap when broken.
Stems: Very short stems arise from a rosette on older plants.
Flowers: Large yellow blossoms mature into round, white puffballs full of seed. The flowers are borne on
ends of hollow stalks.
Seed: The parachutelike seeds are carried many miles by the wind, and a single plant can serve as a continuous
source of infestation.
White Clover (Trifolium repens)
Other names: Clover, Dutch clover.
Growth habit: This cool-season perennial suffocates desirable grasses and goes dormant during hot weather.
The creeping stems root at the nodes and grow close to the ground.
Leaves: Dark green leaves have three leaflets which display white, crescent-shaped marks. The trifoliate
leaves have a long, erect petiole with a membranous sheath at the base.
Stems: Stems that hug the ground and are not cut when mowed.
Flowers: Clusters of white blossoms with a tinge of pink are borne on long stalks. Clusters are 1/2 to 1
1/2 inches in diameter and frequently are visited by bees and other insects.
Seed: Small, heart-shaped seeds may live in the soil 20 years or more.
Summer Annual Broadleaf Weeds
Black Medic (Medicago lupulina)
Other names: Yellow trefoil, black clover, hop medic.
Growth habit: This dark green, warm-season annual grows close to the ground. It can sometimes behave as
a perennial during years when the winter is mild. Black medic is a member of the legume family and has a taproot
that penetrates deeply into most soils. It often is confused with white clover, oxalis, and hop clover.
Leaves: The three-leafed leaflets have prominent, parallel veins, and they are similar to most other clover
leaves. The leaflets are wedge-shaped with a small spur or tooth at the tip. The center leaflet is on a slightly
protruding or extended stem.
Stems: The spreading, prostrate, stems are hairy and do not root at the nodes. Several branches grow out
from the base.
Flowers: Bright yellow flowers (pea-type) are compressed into small, dense clusters. Mature flowers form
a tightly coiled, black seed pod which is strongly veined.
Seed: Each black seed pod contains a single amber-colored seed.
Purslane (Portulaca oleracea)
Other names: Common purslane, pusley, pursley, wild portulaca.
Growth habit: This warm-season annual is drought resistant and can become a troublesome problem in newly
established or thin lawns. The low, prostrate growth habit forms a mat which can shade out several turfgrasses.
Leaves: The bright, shiny green, wedge-shaped leaves are thick, succulent, and often feel rubbery.
Stems: Prostrate, sprawling stems are thick, round, and reddish brown in color. Stems will root wherever
they touch the ground, particularly if the main root has been destroyed.
Flowers: Small, yellow flowers with five petals seldom open unless the sun is shining brightly.
Seed: The cup-shaped seed pod produces an abundance of small, dark rounded seeds. These may lie dormant
in the soil for many years.
Carpetweed (Mollugo verticillata)
Other names: Whorled chickweed, devil's grip.
Growth habit: This slow-germinating, prostrate, warm-season annual spreads rapidly during hot weather. Carpetweed
is of tropical origin, but grows vigorously in Oklahoma.
Leaves: Five to six light green, smooth, slender leaves are grouped together, forming whorls at each node
on the stem.
Stems: The smooth, branched stems are four to six inches long and radiate in all directions from the central
taproot, forming a flat circular mat on the soil surface.
Flowers: Several small, white flowers on short stalks arise from the nodes from May through October.
Seed: Flat, kidney-shaped seeds are a shiny, orange-red color.
Spotted Spurge (Euphorbia supine)
Other names: Eye-bright, milk purslane, milk spurge.
Growth habit: This aggressive warm-season annual grows close to the ground, forming a circular mat that
can eliminate desirable grasses. Few annuals produce as much seed as spotted surge or grow as commonly.
Leaves: Leaves vary in color from a pale, reddish green to dark green. They usually have a maroon spot on
the upper center of the leaf. The opposite and oblong leaves are smooth or sparsely hairy, toothed near the tip,
and on a short petiole.
Stems: Prostrate, spreading stems branch out from a single taproot and do not root at the nodes. A milky
sap is exposed when stems are broken.
Flowers: Very small, inconspicuous, pinkish white flowers arefound in the leaf axils. The fruit is athree-lobed
capsule which develops rapidly.
Seed: Seeds are oblong, three sided, and dark brown or black in color.
Prostrate Knotweed (Polygonum aviculare)
Other names: Knotgrass, doorweed, matgrass, pinkweed, birdweed, stonegrass.
Growth habit: This warm-season annual germinates with the first warm temperatures of spring. The first tiny
shoots of knotweed are often mistaken for crabgrass seedlings. It grows flat from a long white taproot, forming
circular mats that prevent the growth of desirable grasses. Knotweed is well adapted to hard, compacted, worn turf
areas of high traffic. The center playing areas on football fields and areas next to driveways and sidewalks are
some problem locations where knotweed will grow.
Leaves: Smooth, bluish green leaves are one inch long and one-fourth inch wide. They are narrow at the base
with a rounded tip. At the base of each leaf, there is a thin, papery sheath.
Stems: Wiry, non-rooting stems are prostrate and branch quickly forming a circular mat. Enlarged nodes give
the stems a "knotted" appearance.
Flowers: The tiny, white flowers are inconspicuous and are found at the junction of leaf and stem.
Seed: Seeds are small, triangular, and have a dull black color.
Summer Perennial Broadleaf Weeds
Bindweed (Convolvulus spp.)
Growth habit: Vining herb, reproducing by seeds and fleshy creeping rootstocks.
Leaf blade: Elongated, heart-shaped to triangular orate, sharply pointed tip, basal lobes large.
Flower: Bell-shaped to funnel form, white to pinkish.
Curly Dock (Rumex crispus)
Other names: Sour dock, yellow dock, narrow-leaved dock.
Growth habit: This perennial is normally found as a rosette in turf, but it can attain a height of two to
three feet. A thick, brownish taproot penetrates deep into the soil, and growth is most active when the lawn is
under stress from hot, dry weather.
Leaves: Bright, shiny green leaves appear in early spring and later become reddish green in color. Leaves
grow mostly at the base of the plant and are lance-shaped with wavy or curly margins. Leaf blades are six to eight
inches long and one to two inches wide.
Stems: Curly dock remains as a rosette in lawns and seldom produces a stem.
Flowers: This weed seldom produces flower stalks in wellmaintained lawns. When plants grow unchecked, small,
greenish flowers are produced in clusters at the top of the main stems.
Seed: Shiny, reddish brown, triangular seeds are contained within winged pods.
Broadleaf Plantain (Plantago major)
Other names: Door-yard plantain, whiteman's foot.
Growth habit: Cool-season perennial that forms a rosette and is found in poorly managed turfgrasses. Crowds
outdesirable grasses by growing close to the ground.
Leaves: Elliptical leaf blades are often one to three inches wide and three to six inches long. Leaf margins
may be wavy with five prominent veins. The leaves are covered with short hairs that make it rough to the touch.
Flowers: Conspicuous flower stalks are three to six inches long and shorter than buckhorn (P. lanceolata).
Flowers are arranged along more than half of the stem.
Seed: The seeds are brown to dull red and irregularly angled with small lines that run the entire lenath.
Buckhorn Plantain (Plantago lanceolata)
Other names: English plantain, narrow-leaved plantain, riggrass, ribwort, blackjacks.
Growth habit: Widespread perennial broadleaf in poor lawns. Taproot has strong lateral roots from which
a rosette of leaves arises. Cutting or pulling only results in a new plant springing from any part of the severed
root.
Leaves: Long, narrow leaves with three to five parallel veins are three to 12 inches long. Brownish hairs
surround the base of leaves which often twist and curl.
Flowers: A tall, hairy stalk terminates in a cluster of flowers in a tightly compressed cylinder. Several
crops of seed are produced during the season.
Seed: Smooth, shiny seeds are oblong and greenish brown in color.
This chapter includes information reprinted from the OSU Extension manual Turfgrass Pest Management, E-879