A warm-season vigorous grass reaching up to 5 feet, barnyardgrass (Echinochloa crus-galli) has panicles that may vary from reddish to dark purple. The seed heads contain crowded large seeds in spikelets, each with a short, stiff awn. Leaf blades are flat, 3/8 to 5/8 inch wide, smooth, and without a ligule, a papery-like membrane at the collar of the plant where the leaf blade contacts the stem. The stem is flat—not round.
Broadleaf signalgrass
A spreading summer annual, broadleaf signalgrass (Brachiaria platyphylla) has short, wide leaf blades, ranging from 1.5 to 6 inches long and 1/4 to 2/3 inch wide. Leaf blades are typically hairless, except for hairs that occur in the margins and the lower portion of young plants. It doesn’t have a ligule, a papery-like membrane at the junction of the sheath and leaf blade.
Red rice
Red rice is so closely related genetically to commercial rice that anything that will control red rice will generally kill the crop. In fact, it’s the same species—Oryza sativa. Red rice plants vary considerably. The tall-growing, black-hulled, awned plant is easiest to recognize and is considered by many to be a typical red rice plant. However, other strains have developed that have straw-colored hulls, are awnless and are about the same height as desirable rice varieties.
Hemp sesbania
Commonly called coffeebean or coffeeweed, hemp sesbania (Sesbania exaltata) is a tall, blue-green, spindly weed growing up to 12-14 feet. The plants have a yellow, pea-like flower. Seed pods are 4-8 inches long, curved and often tipped with a 0.4-inch-long beak. The leaves are opposite and may feature as many as 70 leaflets with a smooth surface and somewhat hairy surface below.
Alligatorweed
Alligatorweed (Alternanthera philoxeroides) is an aquatic perennial that forms dense floating mats. It has hollow stems, opposite leaves with distinctive midribs and a single white flower head. The leaves are elliptically shaped and 0.2 to 0.8 inches wide.
Yellow nutsedge
Also called yellow nutgrass, yellow nutsedge (Cyperus esculentus) is an aggressive plant that grows between 3 and 32 inches and has adapted to water culture. Distinctive features include a yellow umbrella-like seed head and smooth three-ranked leaves that gradually taper to a small point. Fibrous roots grow from bulbs, rhizomes or tubers. Stems are triangular and rarely branch from the tuber or basal bulb.
Fringerush
Fringerush (Fimbristylis species), also called fan sedge, is an annual often found in the coastal plains. Leaves are flattened, very narrow and up to 12-18 inches long. The seed head is onion-like in appearance with fruiting bodies rounded and scaley.
Dayflower
A crawling, spreading summer annual, dayflower (Commelina communis) grow up to 2 feet. The plant may grow either upright or creeping with numerous branches sprouting at the nodes and stems. Leaves have conspicuous sheaths at the base, and flowers feature two upright blue petals and one smaller white petal. The egg-shaped leaves are 0.3-0.6 inches long and 0.3-1.5 inches wide.
Ducksalad
An aquatic annual or perennial, ducksalad (Heteranthera limosa) grows in open water either near water inlets or in openings in sparse stands. The mature plant grows up to 6 inches tall. Leaf blades may either narrow to a point or be duckbilled at the tip.
Sprangletop
Three species of sprangletop may infest rice fields—Mexican sprangletop (Leptochloa uninervia), bearded sprangletop (Leptochloa fasciculais) and red sprangletop (Leptochloa filifomis). All three are tall with thin, flat leaf blades, running 1/4 to 1/3 inch wide and up to 12 inches long. Sprangletop has a ligule, a papery-like membrane at the collar of the plant where the leaf blade contacts the stem. All three have a large, open panicle when mature.
Texasweed
Although also referred to as Mexicanweed (Caperonia castanifolia), Texasweed (Caperonia palustrus) is a different species. The annual upright plant grows to about 2-3 feet tall with coarse male and female flowers with unique three-capsuled fruit. Leaves are alternating and broad, with serrated edges.
Gooseweed
Sometimes known as chicken spike, gooseweed (Sphenoclea zeylandica) may grow up to 4 feet tall. Leaves grow opposite each other and are spoon shaped and smooth. Stems are hollow and branch above the base. The elliptical leaves vary in size, ranging to about 2 inches wide and 5 inches long. The flowers are borne on a distinctive cylindrical terminal spike.
Annual arrowhead
More of a problem in water-seeded rice, annual arrowhead (Sagittaria montevidensis) is also known as giant arrowhead. The plants, growing up to 20 inches tall, feature arrowhead-shaped leaves and flower petals with green spots. The plants’ only stems are erect, leafless and have only flowers. The leaves arise from the stem base with a stout, spongy stalk and may be up to 8 inches long.
Eclipta
A spindly growing annual weed, Eclipta (Eclipta prostrata) has simple opposite leaves. Leaves measure 3-5 inches long and are elliptical, lacking stalks. Lower surfaces of leaves are hairy. Stems feel sand papery.
Ammannia
Several different species fall under the genera Ammannia and are commonly called purple ammannia, redstem and toothcup. These annual weeds grow upright up to 3-4 feet tall. The stems are square and slightly winged with opposite, ear-like, clasping leaves up to 4 inches long. The flowers are reddish to purple and small, running 0.05 to 0.1 inches long.
Northern jointvetch
Two different species may infest rice fields: Indian jointvetch (Aeschynomene indica) and northern jointvetch (Aeschynomene virginica). Both are upright and usually bushy, growing up to 3-4 feet tall. Indian jointvetch differs from northern jointvetch in that its fruit stalk and leaflets are shorter and its flower smaller. Northern jointvetch plants have large stipules or bracts at the base of the leaf stalk or petiole. Both have pea-like flowers and can be distinguished from hemp sesbania because of a smaller size and more delicate appearance. The alternating leaves have as many as 56 oblong leaflets with smooth edges. Leaflets fold when touched.
A warm-season vigorous grass reaching up to 5 feet, barnyardgrass (Echinochloa crus-galli) has panicles that may vary from reddish to dark purple. The seed heads contain crowded large seeds in spikelets, each with a short, stiff awn. Leaf blades are flat, 3/8 to 5/8 inch wide, smooth, and without a ligule, a papery-like membrane at the collar of the plant where the leaf blade contacts the stem. The stem is flat—not round.
A spreading summer annual, broadleaf signalgrass (Brachiaria platyphylla) has short, wide leaf blades, ranging from 1.5 to 6 inches long and 1/4 to 2/3 inch wide. Leaf blades are typically hairless, except for hairs that occur in the margins and the lower portion of young plants. It doesn’t have a ligule, a papery-like membrane at the junction of the sheath and leaf blade.
Red rice is so closely related genetically to commercial rice that anything that will control red rice will generally kill the crop. In fact, it’s the same species—Oryza sativa. Red rice plants vary considerably. The tall-growing, black-hulled, awned plant is easiest to recognize and is considered by many to be a typical red rice plant. However, other strains have developed that have straw-colored hulls, are awnless and are about the same height as desirable rice varieties.
Commonly called coffeebean or coffeeweed, hemp sesbania (Sesbania exaltata) is a tall, blue-green, spindly weed growing up to 12-14 feet. The plants have a yellow, pea-like flower. Seed pods are 4-8 inches long, curved and often tipped with a 0.4-inch-long beak. The leaves are opposite and may feature as many as 70 leaflets with a smooth surface and somewhat hairy surface below.
Alligatorweed (Alternanthera philoxeroides) is an aquatic perennial that forms dense floating mats. It has hollow stems, opposite leaves with distinctive midribs and a single white flower head. The leaves are elliptically shaped and 0.2 to 0.8 inches wide.
Also called yellow nutgrass, yellow nutsedge (Cyperus esculentus) is an aggressive plant that grows between 3 and 32 inches and has adapted to water culture. Distinctive features include a yellow umbrella-like seed head and smooth three-ranked leaves that gradually taper to a small point. Fibrous roots grow from bulbs, rhizomes or tubers. Stems are triangular and rarely branch from the tuber or basal bulb.
Fringerush (Fimbristylis species), also called fan sedge, is an annual often found in the coastal plains. Leaves are flattened, very narrow and up to 12-18 inches long. The seed head is onion-like in appearance with fruiting bodies rounded and scaley.
A crawling, spreading summer annual, dayflower (Commelina communis) grow up to 2 feet. The plant may grow either upright or creeping with numerous branches sprouting at the nodes and stems. Leaves have conspicuous sheaths at the base, and flowers feature two upright blue petals and one smaller white petal. The egg-shaped leaves are 0.3-0.6 inches long and 0.3-1.5 inches wide.
An aquatic annual or perennial, ducksalad (Heteranthera limosa) grows in open water either near water inlets or in openings in sparse stands. The mature plant grows up to 6 inches tall. Leaf blades may either narrow to a point or be duckbilled at the tip.
Three species of sprangletop may infest rice fields—Mexican sprangletop (Leptochloa uninervia), bearded sprangletop (Leptochloa fasciculais) and red sprangletop (Leptochloa filifomis). All three are tall with thin, flat leaf blades, running 1/4 to 1/3 inch wide and up to 12 inches long. Sprangletop has a ligule, a papery-like membrane at the collar of the plant where the leaf blade contacts the stem. All three have a large, open panicle when mature.
Although also referred to as Mexicanweed (Caperonia castanifolia), Texasweed (Caperonia palustrus) is a different species. The annual upright plant grows to about 2-3 feet tall with coarse male and female flowers with unique three-capsuled fruit. Leaves are alternating and broad, with serrated edges.
Sometimes known as chicken spike, gooseweed (Sphenoclea zeylandica) may grow up to 4 feet tall. Leaves grow opposite each other and are spoon shaped and smooth. Stems are hollow and branch above the base. The elliptical leaves vary in size, ranging to about 2 inches wide and 5 inches long. The flowers are borne on a distinctive cylindrical terminal spike.
More of a problem in water-seeded rice, annual arrowhead (Sagittaria montevidensis) is also known as giant arrowhead. The plants, growing up to 20 inches tall, feature arrowhead-shaped leaves and flower petals with green spots. The plants’ only stems are erect, leafless and have only flowers. The leaves arise from the stem base with a stout, spongy stalk and may be up to 8 inches long.
A spindly growing annual weed, Eclipta (Eclipta prostrata) has simple opposite leaves. Leaves measure 3-5 inches long and are elliptical, lacking stalks. Lower surfaces of leaves are hairy. Stems feel sand papery.
Several different species fall under the genera Ammannia and are commonly called purple ammannia, redstem and toothcup. These annual weeds grow upright up to 3-4 feet tall. The stems are square and slightly winged with opposite, ear-like, clasping leaves up to 4 inches long. The flowers are reddish to purple and small, running 0.05 to 0.1 inches long.
Two different species may infest rice fields: Indian jointvetch (Aeschynomene indica) and northern jointvetch (Aeschynomene virginica). Both are upright and usually bushy, growing up to 3-4 feet tall. Indian jointvetch differs from northern jointvetch in that its fruit stalk and leaflets are shorter and its flower smaller. Northern jointvetch plants have large stipules or bracts at the base of the leaf stalk or petiole. Both have pea-like flowers and can be distinguished from hemp sesbania because of a smaller size and more delicate appearance. The alternating leaves have as many as 56 oblong leaflets with smooth edges. Leaflets fold when touched.