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Barnyardgrass
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.
 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 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.
 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.
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.
 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.
 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.
 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.
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.
 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.
 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.
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.
 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.
Thanks to Dr. Arlen Klosterboer, Texas Extension rice specialist, for reviewing this information and providing the photos.
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