Poisonous plants can cause serious injury to horses, particularly
if animals graze when plants are at an especially dangerous growth stage, when
little other forage is available, and when animals are very thirsty. Poisonings
can be avoided by proper management of animals, pastures, and hay. Suggestions
for preventing poisoning are as follows:
Some of the poisonous plants common to Ohio are described
here. This is not a complete listing, and other sources should be consulted
if you are uncertain as to whether or not a plant could be toxic to your horse.
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BRACKEN FERN (Pteridium aquilinum) - Bracken fern is probably
the largest (up to six feet) and most common of the ferns in Ohio. It
occurs in many habitats, including full sun, partial shade, woods, old
pastures, and thickets. Unlike most ferns, bracken is less common in rich,
moist, limey areas and thus is an indicator of poor soil. The tall, smooth,
grooved stalk supports a large (three-feet long, three-feet wide) leaf
equally divided into three parts, one terminal and two opposite. Each
leaf blade is triangular, with oblong, pointed leaflets, and tight, narrow,
blunt-tipped sub-leaflets. On fertile leaves the underside has a continuous
line of sporangia around the leaf edge, covered by the overlapping margins.
Bracken is one of the earliest ferns to appear in spring or after a fire.
It sometimes forms large colonies of nearly solid stands, with the dark,
green, leathery leaves bending nearly horizontal. In the fall, it is one
of the first plants to be killed by frost, leaving large patches of crisp,
brown foliage.
Horses eating large quantities of bracken fern show signs of acute poisoning
related to vitamin B1 deficiency. Leaves as well as rhizomes are toxic.
Poisoning is most common when other grazing is scarce, such as after periods
of drought, or when bracken is a contaminant of hay. Symptoms usually
appear two to four weeks after continuous grazing. Horses are particularly
susceptible to bracken fern poisoning. Affected animals exhibit loss of
condition and weight, incoordination, and a crouching position with feet
apart and arched back. Bracken fern poisoning may be confused with other
disorders, and other plants (field horsetail, turnip) can also induce
symptoms related to B1 deficiency. Bracken fern can be suppressed or eliminated
from pastures by improved pasture management that includes periodic close
grazing or cutting and proper fertilization.
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FIELD HORSETAIL (Equisetum arvense) Field horsetail is
the most common of several horsetails and it is also the most variable.
This is a unique plant with two distinct growth forms (sterile and fertile
stems), which often are not found together. The sterile stems are light
green, highly branched, resembling a small pine tree. Stems are ascending
and appear to be leafless; they may be perennial and evergreen, or annual,
dying in autumn after frost. The stem has distinct joints or nodes, which
bear tiny, black, scalelike leaves. The fertile stems are singular, tall,
dark green, ridged, hollow, tubular, and distinctly jointed. Branches,
when present, arise singly or in whorls at nodes. The stem terminates
in a cone-shaped spore-bearing strobilus. The stem is rough like sandpaper
due to impregnation with silica. The plant reproduces by spores or by
deep, creeping rootstocks which sometimes bear tubers.
Field horsetail is found throughout Ohio along railways, field edges,
woods, and waste areas. It seems to tolerate poor drainage and sandy or
gravely areas. This weed is difficult to exterminate as it tolerates most
herbicides.
Field horsetail causes most trouble in hay fed to horses. Poisoning is
similar to bracken fern poisoning; however, horsetail-poisoned animals
maintain their appetites even after clinical signs appear. The poisoning
is associated with thiaminase activity and thus vitamin B1 deficiency.
Affected animals exhibit loss of condition, unthriftiness, excitability,
staggering, and emaciation.
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TALL FESCUE (Festuca arundinacea) Tall fescue is probably
the most widely adapted perennial pasture grass. It is a tall (up to five
feet), tufted, deep-rooted plant that forms a coarse sod. Leaves are about
one-quarter inch wide, with a ridged surface and fine, sharp, saw-toothed
edges. The inflorescence is a compact panicle four- to 10-inches long.
Although fescue poisoning is a condition of cattle, summer fescue toxicosis
can affect horses during summer when grazing or fed tall fescue forage
or seed. Toxin is produced in tall fescue forage or seeds contaminated
with an endophytic fungus. Affected animals show reduced feed intake and
weight gains. Within one or two weeks after fescue feeding has begun,
other signs such as fever may appear. Failure to produce or let down milk
can be a problem in mares grazing endophyte-infected fescue. The severity
of the toxin may vary from field to field, but increases when temperatures
exceed 75 to 80ºF, and where high rates of nitrogen fertilizer have
been applied to the grass. Tall fescue varieties are available that do
not contain the endophyte; toxic pastures should be destroyed and planted
to nonendophytic fescue varieties.
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PERENNIAL RYEGRASS (Lolium perenne) Perennial ryegrass
is a smooth, shiny, short-lived perennial with slightly flattened stems.
Leaves have well-developed auricles (on most leaves) and membranous ligules
that may be toothed or rounded. It favors moderately moist open ground
and is common in Ohio.
Perennial ryegrass infested with an endophytic fungus can be the source
of a neurotoxic condition (perennial ryegrass staggers) that occurs only
in summer and fall. The fungus occurs in all parts of the plant, especially
leaf sheaths, culms, and seeds. Affected animals exhibit fine tremors
of the head and nodding movements. Well-grazed, leafy pastures that do
not go to seed or are not overgrazed are less likely to be dangerous.
Endophyte-free varieties should be used for pasture renovation.
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WATER HEMLOCK (Cicuta maculata) Water hemlock is one of the
most poisonous plants in Ohio. It occurs in almost all counties on the
shores of lakes, ponds, marshes, bogs, and wet ditches. It is an erect
perennial growing to eight-feet tall. Stems are smooth, hollow (except
at nodes), and streaked with purple lines (not blotched as in the less
dangerous poison hemlock, Conium maculatum). Water hemlock leaves are
divided into three to seven lanceolate leaflets with irregular, coarsely
toothed margins. Flowers are borne in an open umbel resembling that of
wild carrot. The most distinguishing characteristic is the swollen base
of the plant and rootstocks. Splitting open one of these areas reveals
crosswise partitions that divide the rootstock into chambers.
The yellow, oily fluid exuding (especially in springtime) from a cut
stem base or rootstock contains the toxic alcohol, cicutoxin. All parts
of the plant contain the toxin and are considered dangerous. Livestock
have been poisoned by drinking water standing in small pools where the
plant has been tramped and the roots crushed. Poisoning is most common
when the plant is young, somewhat succulent, and growing rapidly. Symptoms
range from nausea and colic to violent convulsions and death (especially
in cattle).
The appearance of water hemlock is very similar to poison hemlock, page
72.
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COMMON POKEWEED (Phytolacca americana) Common pokeweed
is a simple, erect, herbaceous perennial that sometimes resembles a small
tree, growing up to 10 feet in height. Common pokeweed emerges each year
from a large taproot or from seeds. The base of the pokeweed stem is typically
deep red-purple in color. The smooth, hairless, hollow, fleshy stem can
attain diameters of four inches. The large elliptical leaves range from
12- to 20-inches long. They are about a third as wide as they are long.
The leaves are alternate on the stem and are hairless. Flowers are in
dense, drooping clusters with white-green petals that bloom from July
through August. Flower clusters occur opposite a leaf. From a distance,
the purple fruit resembles a bunch of grapes that hang down from the point
of attachment on the plant. Common pokeweed is found throughout Ohio in
clearings and open woods and is becoming more abundant in reduced tillage
fields.
Pokeweed is a plant that will cause severe poisoning and is one that
livestock will not avoid eating. The thick, woody roots of pokeweed are
the most poisonous part of the plant and account for most livestock poisonings.
The fruit of pokeweed is the least toxic part of the plant, but may be
responsible for human deaths. The toxic compound is an alkaloid called
phytolaccotoxin. Horses can be poisoned by eating fresh leaves or green
fodder. Symptoms of poisoning from pokeweed include burning sensations
in the mouth, gastrointestinal cramps, vomiting, and diarrhea.
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COMMON COCKLEBUR (Xanthium strumarium) This native annual
weed is troublesome in agronomic crops and is especially common on rich,
moist soils. The plant is rough in appearance, branched, hairy to nearly
smooth, with irregular mottled stems. The mature plant is one- to two-feet
tall. The thick, rough leaves are alternate, broadly ovate to triangular,
with long petioles. Flowers are relatively inconspicuous, on short axillary
branches. The fruit is a bur with strong, hooked spines and two sharp-pointed
beaks.
The seeds are toxic but are seldom consumed because of the burs, which
are too spiny to ingest. The tender, juicy cotyledons, which are long
and narrow, contain carboxyatractyloside, which affects the nervous system.
Signs of poisoning include anorexia, depression, and weakened heartbeat.
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HEMP DOGBANE (Apocynum cannabinum) Hemp dogbane, Indian
hemp, choctaw root, rheumatism weed, and snakes milk are names for
this native perennial weed that is common in all counties of Ohio. Hemp
dogbane is an erect plant that grows one- to four-feet tall and reproduces
by creeping roots and by seeds. The leaves are two- to six-inches long,
opposite, oval, and attached to the stem by a short petiole. Leaf edges
and upper surface are smooth, while the underside of the leaf is finely
hairy. Hemp dogbane branches freely, unlike common milkweed, with which
it is often confused. All parts of the plant contain a milky latex. Shoot
emergence from roots typically occurs from late-May to mid-June. The flowers
of hemp dogbane are greenish-white, five-petaled, and inconspicuous. Hemp
dogbane produces reddish-brown, paired sickle-shaped pods that are four-
to eight-inches long and hang from the point of attachment. A related
poisonous species, spreading dogbane (A. androsaemifolium), has slightly
drooping leaves and larger, pink, bell-shaped flowers.
Leaves and stems of green and dry plants contain a resinoid and a glucoside
with cardioactivity. Less than an ounce of green or dry leaves may be
enough to kill a horse. Symptoms of poisoning include increased temperature
and pulse, sweating, dilated pupils, discolored mouth and nostrils, and
refusal to eat or drink. Hemp dogbane can be a threat to livestock in
all seasons.
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WHITE SNAKEROOT (Eupatorium rugosum) This plant is a common
perennial of shady, moist woodlands and wood edges. It often goes unnoticed
because flowering does not begin until July or later. Stems are tall and
mostly smooth, with opposite, long-petioled leaves. Leaf blades are generally
egg-shaped, with sharply toothed margins and three prominent veins. Small
white flowers are borne in loose spreading clusters.
The toxic compound, tremetol, is found in the leaves and stems of white
snakeroot and is at peak concentrations in summer through fall. Tremetol
is unusual in that it is a fat-soluble molecule that becomes concentrated
in the milk of lactating animals. Signs of poisoning begin with trembling
in the leg muscles. Other symptoms include sweating, labored and rapid
breathing, constipation, depression, stiff gait, dilated pupils, and weakness.
Death may be sudden.
Milk sickness, caused by drinking milk produced by animals that have
eaten white snakeroot, is of historical significance because this affliction
reportedly killed Abraham Lincolns mother.
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YELLOW SWEETCLOVER (Melilotus officinalis) and WHITE SWEETCLOVER
(Melilotus alba) Both species of sweetclover are widely distributed
throughout the state, having been introduced in the United States long
ago as a hay, pasture, and green manure crop. The sweetclovers are erect,
slender, branched biennials that can grow as tall as nine feet. Leaves
are clover-like, with three oblong leaflets that are toothed around the
entire margin. Flowers are small, white or yellow, and fragrant; they
appear in long, slender clusters at branch tips or arising from leaf axils.
Fruits are ovoid, smooth pods with one to four seeds. The plant is commonly
found along roadsides, railroad tracks, open fields, and waste areas.
As a forage crop, sweetclovers can be freely grazed, but feeding moldy
sweetclover hay or silage is dangerous. Thus, sweetclover poisoning usually
occurs in winter and is not apparent until animals have been fed damaged
sweetclover hay for two or more weeks. Well-cured hay is not dangerous,
but absence of visible spoilage does not necessarily mean the hay is safe
to feed.
Poisoning results from the process of spoiling, or molding, wherein harmless
natural coumarins are converted to toxic dicumarol. The most dangerous
hay is the outer portion of weathered, large round bales. The main sign
of poisoning is hemorrhaging, which results from faulty blood coagulation.
The toxic compound crosses the placenta and may affect newborns.
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COMMON MILKWEED (Asclepias syriaca) Common milkweed is
an erect perennial that reproduces by creeping roots and seeds. Stems,
reaching three to six feet in height, are unbranched and covered with
short downy hairs. The leaves are oblong, three- to eight-inches long,
with a rounded to tapered leaf tip and base. Leaves are opposite and are
attached directly to the stem. The underside of the leaves are covered
with fine velvet-like hairs. The upper surface, which can be hairless
or hairy, shows a prominent white midrib. The secondary veins off the
midrib resemble the rungs of a ladder. Young seedlings and emerging vegetative
shoots of common milkweed are covered with downy hairs, thus differentiating
them from hemp dogbane. The milkweed family is known for a white milky
sap that appears when the plant is bruised or cut open. Flowers are borne
in a large ball-like cluster and are sweet-smelling, pink-lavender in
color, and bloom from June to August. The gray, rough, spiny pods are
three- to five-inches long, one-inch wide, and split on one side. The
seeds inside of the pod are brown, flat, and oval. They resemble an enclosed
horseshoe with an attached downy pappus (silky structure similar to that
of dandelion). Common milkweed is native to North America and is found
throughout Ohio. It grows best in warm, dry soils with full sunlight and
is commonly found growing in clumps or patches on roadsides and in reduced
tillage fields.
All parts of the plant, whether green or dry, are poisonous to horses.
The toxic principles are steroid glycosides and toxic resinous substances.
Livestock generally avoid this plant unless other forage is unavailable.
Signs of poisoning include dizziness, loss of muscular control, violent
spasms, rapid and weak pulse, respiratory paralysis, and rarely death.
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MUSTARDS (Brassica) spp., (Raphanus) spp., and related genera
The mustard family (Cruciferae) comprises a large group of herbaceous
plants, most of which are annuals, winter annuals, or biennials. Flowers,
with four sepals, four petals, and six stamens (two short and four long)
are yellow or white, and arranged in racemes. Fruits are borne in two-chambered,
flat-round, or beaked tubular capsules. Basal leaves are generally lobed
or coarsely toothed. Mustards are found throughout Ohio along roadsides,
waste areas, open fields, and pastures. Seeds of many species live a long
time in the soil, and seedlings reappear after many years when soil is
disturbed.
Many mustards are harmless when young and are grazed without incident.
However, seeds and vegetative parts (fresh and dry) may contain the toxic
principle glucosinolate (isothiocyanate). Feeds containing grain screenings
with a large number of mustard seeds may be dangerous to horses. Mustard
oils, which are released by enzymes when mustard seeds are moistened with
cold water before feeding, are strong irritants.
Signs of poisoning include acute/chronic anorexia, severe gastroenteritis,
salivation, diarrhea, paralysis, photosensitization, and hemoglobinuria.
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POISON HEMLOCK (Conium maculatum) Poison hemlock is a tall,
erect biennial that produces a vegetative rosette the first season of
growth and an upright reproductive stem in the second season. Stems are
mostly hairless and light gray-green with distinct reddish-purple spots.
They are hollow, except at the nodes, and grow to 10-feet tall. Leaves
are basal in the rosette stage and alternate on the stem in the reproductive
stage. The basal and stem leaves are finely dissected with a lace-like
appearance, resembling the nonpoisonous wild carrot. The flower heads
at the top of the plant are large, one to three inches in diameter, white,
and umbrella-shaped. Flowers develop into a green, deeply ridged fruit
with several seeds. The plant has an unmistakable and disagreeable mouse-like
odor.
Poison hemlock was introduced from Eurasia as an ornamental plant and
is currently found in about half of the counties in Ohio. It grows in
waste areas, especially partially shaded, poorly drained sites, stream
banks, or edges of cultivated fields. Seeds germinate in autumn, and seedlings
grow late into fall. It is one of few green plants in pastures in late
winter and is among the first plants to green up in the early spring.
This plant is sometimes confused with wild carrot or wild parsnip.
All parts of this plant are poisonous, though roots are more toxic than
leaves or stems. Leaves are especially poisonous in the spring, whereas
the root becomes more toxic over time. Eight alkaloids are found in this
plant, with coniine and conicine being the most common. Livestock can
be severely injured by eating the leaves or fruits of poison hemlock.
The strong odor usually prevents consumption of the green plant, but animals
can be poisoned by eating contaminated fresh hay or silage. Signs of poisoning
include dilated pupils, weakness, staggering gait, and respiratory paralysis
two to three hours after ingestion.
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COMMON ST. JOHNSWORT (Hypericum perforatum) Common St.
Johnswort is a creeping perennial that reproduces by seeds and spreading
underground roots. This species has hairless, branched reddish stems with
a woody base and grows up to three-feet tall. St. Johnswort is characterized
by its small (one-half to one-and-one-half inches long) oval, opposite
leaves and large stomata that appear as small perforations or holes in
the leaves when held up to the light. The leaves are attached directly
to the stem. Distinct bright yellow flowers (three-quarters to one inch
in diameter) with many stamens are numerous and may have black dots on
the edges of the petals. The fruit is a three-celled capsule with many
dark brown seeds. When wet, the seeds have a gelatinous coating that sticks
them to objects (e.g., animal legs, hooves, machinery).
Common St. Johnswort, also called klamathweed or goatweed, is an introduced
species native to Eurasia. It is common in the eastern part of Ohio, but
is sporadically distributed in western Ohio. This species is commonly
found in old meadows, pastures, roadsides, waste areas, and in reduced
tillage agronomic systems. In total, there are 16 different species of
Hypericum in Ohio. The name Hypericum is from a Greek word meaning "over
an apparition," alluding to its ancient use as an herb to protect
one from evil spirits. The species name, perforatum, refers to the perforated
look of the leaves.
Leaves and flowers of common St. Johnswort contain a photodynamic pigment
called hypericin, which causes "photosensitization" on white
or light-colored skin. Photosensitization is especially prevalent on areas
of the body which receive the most sunlight, such as the head, neck, and
back. Affected skin becomes swollen, tender, and reddened (erythema),
and large areas may peel off. Other signs of poisoning include loss of
appetite, severe itching, blindness, convulsions, hypersensitivity to
cold water, and coma. The plant is dangerous at all growth stages. Grazing
animals may also suffer minor skin irritations that include skin blisters
and hair loss. If enough of this plant is ingested, death may result.
The toxic properties of St. Johnswort remain when it is a contaminant
of hay.
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GROUNDSELS (Senecio) spp. There are eight species of Senecio
recognized in Ohio, the most poisonous being the relatively uncommon cressleaf
groundsel (S. glabellus), also called butterweed or yellowtop. Cressleaf
groundsel is an erect biennial reaching heights of one to three feet.
The stem is succulent, smooth, and hollow, and it branches at the top
to support flowers. Leaves are alternate, deeply divided, with wide, round-toothed
lobes. Basal and lower leaves are up to eight-inches long; upper leaves
are smaller but similar in shape. Bright lemon-yellow flowers, up to one
inch in diameter, are borne in clusters and bloom from April to June.
Cressleaf groundsel occurs in wet woods, swamps, streambanks, wet ditches,
and pastures. The weed is uncommon, but is known to spread quickly. The
related weedy species, common groundsel (S. vulgaris), is more common,
and is distinguished by the absence of ray flowers and a solid, shorter
stem. Common groundsel is found in fields and waste places.
Groundsel species contain pyrrolizidine alkaloids (e.g., senecionine),
which cause irreversible liver damage with prolonged exposure. All parts
of common groundsel contain toxins; however, toxin concentrations are
greatest in the flowers, and in the leaves just before flowers reach maturity.
Obvious signs of poisoning often do not appear until liver damage is severe.
Early symptoms include anorexia and depression and are followed by incoordination,
diarrhea, presence of hemoglobin in the urine, cirrhosis of the liver,
and death.
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JOHNSONGRASS (Sorghum halepense) Johnsongrass is a tall
(up to 10 feet) coarse-textured perennial grass that reproduces by rhizomes
and seeds. Leaves are rolled in the bud and have a tall membranous ligule
with shallow teeth on the top. Leaf blades are long (eight to 24 inches),
smooth, and flat, with a thick, prominent white midvein. Leaves are usually
bright green, but they may also contain purple pigmented spots. In the
vegetative stage, Johnsongrass looks like a narrow-leaved corn plant.
The seedhead is large, purple, and pyramidal in shape, with dark reddish-brown,
oval seeds.
Johnsongrass was brought to United States from the Mediterranean as a
contaminant of crop seeds. It is named for Colonel William Johnson who
introduced this species on his farm in Alabama around 1840. Johnsongrass
is often found in many Ohio counties, especially along irrigated canals,
fields, and other areas with rich soils. This species is considered among
the worlds 10 worst weeds.
Hydrocyanic acid (cyanide) is produced in the leaves and stems of Johnsongrass
when it is subjected to drought, trampling, frost, herbicide treatment,
and even cutting. Toxicity is identical to that of Prunus poisoning and
results in hypoxia (deficiency of oxygen reaching the tissues). The first
symptoms appear within a few minutes following ingestion. Affected animals
exhibit excitement, incoordination, convulsions, rapid and labored breathing,
bloating, and coma. Death can occur in less than an hour due to internal
asphyxiation.
Toxic levels of nitrates can accumulate in Johnsongrass following heavy
fertilization or drought and result in toxicosis which may be confused
with cyanide poisoning. Common symptoms of nitrate poisoning include stomach
and intestinal irritation and may result in hypoxia (deficiency of oxygen
reaching the tissues).
Horses are less susceptible to cyanide and nitrate poisoning than are
ruminants.
SORGHUMS (Sorghum vulgare, Sorghum vulgare sudanense) and hybrids
Sorghums are tall (up to eight feet), coarse, annual grasses with
large terminal panicles. There are numerous varieties, some of which are
cultivated for forage, syrup, broom, or grain production. Under unfavorable
conditions, all may be poisonous.
As with Johnsongrass, hydrocyanic acid is produced in sorghum in response
to drought, trampling, frost, or second growth, and nitrates accumulate
with heavy fertilization or drought. Affected animals exhibit signs of
hypoxia, including difficulty breathing, bloat, staggering, convulsions,
and death. Sorghum poisoning is especially a problem in horses following
grazing of sorghum pastures for several weeks to months.
The appearance of sorghums is very similar to Johnson Grass, page 75.
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NIGHTSHADE FAMILY
The Solanaceae, or nightshade family, contains several important poisonous
plants. The toxic principle is the same for all. The glycoalkaloid, solanine,
is produced in leaves, shoots, and unripe berries, and causes gastrointestinal
irritation and central nervous system problems. Symptoms of poisoning
include acute hemorrhagic gastroenteritis, weakness, incoordination, difficulty
breathing, excess salivation, and death.
The most important species in Ohio are eastern black nightshade, bittersweet
nightshade, horsenettle, and two species of groundcherry. The common potato
can also be dangerous, in that white sprouts and green parts of the plant,
especially green skinned tubers, are poisonous. Identifying features of
the weedy species are given here.
Eastern black nightshade is an example of the nightshade family. See
page 77.
EASTERN BLACK NIGHTSHADE (Solanum nigrum) is an erect annual.
Leaves are coarsely and shallowly toothed, with slight pubescence on the
undersurface. Flowers are white to purple and are borne in an open cluster.
The juicy, many-seeded berries are initially green, ripening to purplish
black. Eastern black nightshade is widespread in Ohio and is found along
stream banks, thickets, roadsides, row crop fields, and other open, disturbed
habitats.
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BITTERSWEET NIGHTSHADE (Solanum dulcamara) is also known as European
bittersweet, poison berry, climbing nightshade, and deadly nightshade.
It was introduced from Eurasia as an ornamental and is now distributed
throughout Ohio. It is found in hedgerows, ditches, waste areas, and open
fields, especially areas that tend to be moist or even waterlogged for
a portion of the year. Bittersweet nightshade is a creeping perennial
vine that spreads by rhizomes and reproduces by seed. Leaves are arranged
alternate on a dark red to black woody stem. The leaves are of two forms
one is simple and ovate and the other is similar with additional
basal lobes. Both forms are two to four-and-one-half inches in length,
have smooth leaf margins, and are a dark green color with a purple tinge.
Leaves may be either with or without hair. Flower clusters branch from
the main stem. Flowers are one-half inches in diameter, with five purple
petals that join together to form a star-shape with a yellow center. Fruits
are oval green (immature) to red (mature) berries and are thin-skinned
with many flat, yellow round seeds. Leaves, stems, and berries can be
poisonous.
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HORSENETTLE (Solanum carolinense) is sometimes called bull nettle,
devils potato, or wild tomato. It is an erect creeping perennial
weed that spreads by rhizomes and reproduces by seeds. Horsenettle is
characterized by hard sharp yellowish spines found on the stems and leaves.
Leaves are alternate, finely hairy on both surfaces, egg-shaped (one-and-one-half
to five-and-one-half inches long and three-quarters to two-and-one-half
inches wide), with very coarsely toothed margins, resembling a poinsettia
leaf. Flowers are star-shaped with five white to violet petals with bright
yellow anthers. Fruits are green when young and turn to yellow-orange
and wrinkle as they mature. Berries contain many round, flat, yellow to
orange seeds. Horsenettle is native to the southeastern United States
but is distributed throughout all Ohio counties. It is commonly found
in pastures because most animals will avoid eating it; it is also found
in waste areas and open fields. All parts of the plant are poisonous,
with the level of solanine highest in the fall.
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GROUNDCHERRIES include seven species of the genus Physalis which
have been found in Ohio, the most common being smooth groundcherry (P.
longifolia var. subglabrata) and clammy groundcherry (P. heterophylla).
The main difference between the two species is that the former is smooth
and the latter is densely hairy. Both species are found in almost all
counties of Ohio and are sometimes called hog-plum, husk-tomato, or wild-pompion.
They are commonly found in cultivated and reduced tillage agronomic fields,
as well as in pastures, along roadsides, and in waste areas. Both groundcherry
species are erect perennials growing one to three-feet in height. They
reproduce by seed and vegetatively by creeping roots. Stems are ridged
and hollow, with spreading branches. Leaves (two- to four-inches long
and three-quarters to one-and-one-half-inches wide) are alternate, unevenly
toothed, and approximately diamond-shaped, tapering towards the petioles.
Flowers are bell-shaped with a yellow corolla (one-half inches in diameter)
that may have a violet-spotted center. A five-sided lanternlike pod hangs
from the plant and encloses a berry or groundcherry. The fruit is a green
to purple fleshy berry approximately one-half inch in diameter, with many
kidney-shaped seeds. Leaves and unripe fruit are poisonous.
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JIMSONWEED (Datura stramonium) is a foul-smelling coarse annual.
Stems are erect, up to four feet tall, smooth to slightly pubescent, and
green to purple. The leaf shape resembles that of poinsettia, with irregular,
coarsely toothed to shallowly lobed margins. Flowers are borne singly
on short stalks in the axils of branches. The flower is a white to purple
five-angled tube with a spreading, toothed, plaited border. The funnel-shaped
flower is two- to five-inches long and one to two inches across. The fruit
is a distinctive, hard, prickly, many-seeded capsule splitting into four
sections.
The plant is native to the tropics but is naturalized throughout Ohio.
It is common around barnyards, feedlots (especially hog lots), cultivated
fields, roadsides, and other disturbed habitats. Other names for this
weed are thorn-apple and jamestown-weed.
All parts of the plant, and seeds in particular, contain tropane alkaloids
(atropine, scopolamine, hyoscyamine). Because of the strong odor and taste,
animals seldom consume enough of the green plant to be affected, but poisonings
result from eating the dry plant in hay or silage, or from seeds mixed
with grain. Affected animals may exhibit a weak, rapid pulse, dilated
pupils, dry mouth, incoordination, diarrhea, convulsions, coma, and sometimes
death.
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