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University Library, University of Illinois at Urbana-Champaign

Plants Toxic to Animals

H

Hyacinth orientalis (Hyacinth)

Hyacinth blossomsDescription

Hyacinth is one of all the early spring blooming flowers most favored by home gardeners. It is a bulbous herb

Hyancinth Bulbsof the lily family with its origin in the Mediterranean region and cultivated in many color varieties. Green leaves, 7-8 per bulb, all arising from the ground level, are fleshy, glossy, narrow with smooth margins, 4-12 inches long and about 3/4 inches wide without marginal teeth. Flowers, borne in a dense raceme on a 6-8 inch long stem, are bell-shaped, and eventually open into 6 reflexed tepals. The flower is most well known for its fragrance. Fruits are globose and have 3 divisions. The bulb is 1-1/2 to 2 inches in diameter, light purple or cream colored, and covered with dry skin-like layers.

Distribution

Hyacinths are often potted and grown inside or grown outdoors in gardens.

Conditions of Poisoning

The poisonous principle is concentrated in the bulb. Ingesting only a small amount of the bulb may cause stomach upset. Keep the bulbs out of the reach of animals, particularly dogs, cattle, and pigs. Other plant parts are also poisonous, but are less concentrated than in the bulb.

Toxic Principle

Contains calcium oxalate raphides in what appears to be ejector cells (similar to Araceae plants) and alkaloids such as lycorine. Both bulbs and plants may be irritating to the skin and gastrointestinal tract.

Clinical Signs

Hyacinth poisoning is very rare. Clinical signs usually include digestive tract disorders such as colic, vomiting and diarrhea. Skin irritation from contact is possible, although usually minor. Allergic asthma and nasal irritation in susceptible individuals.

Animals Affected

Dogs, cattle, pigs, cats, horses

References Used

https://plants.ces.ncsu.edu/plants/all/hyacinthus-orientalis/

Hydrangea spp. (Hydrangea)

Pink Hydrangea blossomDescription

The cultivated species, Hydrangea macrophylla Ser. (= H. hortensis), is a deciduous shrub which can reach nearly 6 feet. The common cultivated species is grown widely in gardens and as potted plants. The flowers among the cultivated species include white, pink, mauve, bluish purple, to blue. The forms of the flower clusters and the leaves of the cultivated species are similar to those of the cold-hardy wild species (H. arborescens L.).

Wild hydrangeas, H. quercifolia Bartr. and H. arborescens L., are shrubs which reach from 3.5 to 10 feet in height. The stems are light green when new, turning light brown and woody with time. Leaves are alternate, 4-10 inches in length, dark green above, lighter or pale green on the underside. The leaves of H. quercifolia Bartr. are deeply lobed, while those of the other species (H. arborescens L.) are broadly rounded with apex tapering to a point. Flowers appear in clusters or heads, mostly with 4 petals in white or cream color, blooming from June to July. The capsular fruit is less than 1/8 inch in length and has many small, thin brown seeds.

Distribution

Though wild hydrangeas are sometimes grown as ornamental shrubs in gardens, H. arborescens L. is widely distributed in wooded areas, rarely in full sunlight, from New York to Georgia, west to Kansas and Oklahoma including the southern half of Illinois. H. quercifolia Bartr. is limited to the southeastern states and usually grows in considerable shade on river bluffs and steep banks of sinkholes.

Conditions of Poisoning

Generally poisoning is rare and only occurs after eating large quantities of the plant, but a horse was seriously poisoned after eating a single potted hydrangea.

Toxic Principle

May contain the cyanogenic glycoside hydrangin, but cyanide intoxication is rare and poisonings do not generally involve effects or clinical signs of typical cyanide.

Clinical Signs

Affected animals may experience painful gastroenteritis, and diarrhea which may be bloody.

Animals Affected

Dogs, cats, horses

References Used

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/hydrangea

Hypericum perforatum L. (St. John's Wort)

Description

St. John's Wort is an herbaceous perennial that is erect and grows up to 3 feet tall. It has many opposite branches and an extensive rhizomatous root system. The leaves are opposite, elliptic to oblong, and may have tiny, dot-like translucent or black glands. The flowers are bright yellow, star-shaped with five petals that have black dots on the margins, and have many stamens.

Distribution

St. John's Wort is found as a weed throughout most of North America, but it is particularly common in the northwest. It grows in dry, disturbed soils such as roadsides, fields, and waste spaces. It is also intentionally cultivated for use as an herbal medicine to treat depression, anxiety, and insomnia.

Conditions of Poisoning

Poisoning occurs after the plant is ingested and the animal is exposed to sunlight. Drying does not inactivate the toxin, so ingesting hay made from St. John's Wort can also produce symptoms. The young plants are as poisonous as the mature plants and seem to be more palatable to livestock. The amount of toxin present in the plant is dependent on the growing conditions of the plant and can vary.

Control

Animals should not be allowed to graze in areas where St. John's Wort is present, particularly animals with light skin or which lack a heavy layer of fur that will block sunlight.

Toxic Principle

Hypericin, which is a photoreactive pigment contained in the glands found on the leaves and flowers. The highest concentration of hypericin is found in the black glands, while the transparent glands contain protohypericin. Poisoning in cattle occurs after consuming about 1% of their body weight, while sheep must eat about 4% of their body weight to develop symptoms. 

Clinical Signs

Photosensitization, skin reddening, swelling, ulcers, sloughing of skin. Symptoms only develop when the poisoned animal is exposed to sunlight, and are generally limited to areas of the animal that are lightly pigmented or do not have thick fur to block sunlight.

Animals Affected

Humans, cattle, sheep, horses, cats, dogs

References Used

Knight, A. P., & Walter, R. G. (2001). A guide to plant poisoning of animals in North America. Jackson, Wyo.: Teton NewMedia.

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/st-johns-wort

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=e198

https://csuvth.colostate.edu/poisonous_plants/Plants/Details/43

K

Kochia scoparia (L.) Schrad. (Fireweed)​

Description

Fireweed is known by many names including Summer Cypress, Burning Bush, and Mexican Fireweed. Fireweed can be grown in dry drought conditions. In ideal conditions, it grows to six feet high. The plant's stems have many branches with soft, fluffy leaves. The flowers are green and unnoticeable, growing in the axils of the upper leaves. The veins of the leaves, as well as mature stems, are typically red. The stems change to bright red in the fall. 

Distribution

Fireweed is found throughout the western and northern United States, as well as in much of Canada. It is common along roadsides, the edges of fields, and the edges of waste areas.

Conditions of Poisoning

Fireweed can affect many biological systems of livestock, including the cardiovascular system, respiratory system, nervous system, renal system, integumentary system, ocular system, and hepatic system. Immature Fireweed is often used in livestock's feed because it has a similar composition to alfalfa. When consumed in large quantities, mature Fireweed can cause nitrate poisoning. 

Control

Individuals should contact their local agriculture extension specialist or county weed specialist for guidance in the best practice for managing Fireweed in their area.  Herbicides tend to be less effective as Fireweed matures; their general effectiveness depends on the size of the dose used and the age of the plant. 

Toxic Principle

Toxicity of the plant can change depending on growing conditions; more mature plants or plants growing in extreme drought can be more toxic to animals. In general, Fireweed can produce nitrates, sulfates, saponins, and alkaloids. 

Clinical Signs

Livestock will show different symptoms of Fireweed poisoning depending on the biological system affected. Commons symptoms are difficulty breathing, blindness, depression, kidney failure, and liver disease. In cases of severe nitrate poisoning, livestock can die. 

Animals Affected

Sheep, horses, cattle

References Used

https://plants.usda.gov/plantguide/pdf/pg_kosc.pdf

https://csuvth.colostate.edu/poisonous_plants/Plants/Details/84

L

Lantana camara L. (Lantana)

Description

Lantana (yellow sage) is a native of tropical Americas and West Africa. In the northern states including Illinois, it is grown as a garden annual reaching 12-18 inches tall. In the south, from Florida to California, it grows as a perennial shrub of 3-6 feet tall. In the tropics, it may grow even taller. Leaves are opposite, ovate, 1-5 inches long and 1-2 inches wide, with very small rounded teeth, somewhat rough and hairy. Leaves are aromatic when crushed. Flowers are borne in dense clusters 1-2 inches across on the axils near the top of the stem. Each flower is tubular with 4 lobes flaring to about 1/4 inch, initially yellow or pink gradually changing to orange and deep red. Often, the different colored flowers are present on the same cluster. Fruit is fleshy, greenish-blue to black, and berry-like with each containing one seed.

Distribution

Lantana is commonly found along roadsides, fence rows, and in fields in Florida and southern California where it escaped cultivation. In the northern U.S., it is strictly a garden and greenhouse annual. 

Conditions of Poisoning

Animals in pastures with sufficient forage will often avoid Lantana, perhaps because of its pungent aroma and taste, but animals unfamiliar to the plant may ingest enough to affect them. Fifty to ninety percent of animals newly exposed may be affected. Foliage and ripe berries contain the toxic substances with the toxins being in higher concentrations in the green berries.

Toxic Principle

Lantana contains lantadene A and B (the major toxins involved in poisoning) as well as other structurally and toxicologically related pentacyclic triterpene acids, including reduced lantadene A, dihydrolantadene A, and icterogenin.

Clinical Signs

The major clinical effect of Lantana toxicosis is photosensitization, the onset of which often takes place in 1 to 2 days after consumption of a toxic dose (1% or more of animal's body weight). Jaundice is usually prominent, animals usually become inappetent, and they often exhibit decreased digestive tract motility and constipation. Other signs may include: sluggishness, weakness, and transient, sometimes bloody diarrhea. In acute cases, death occurs in 2 to 4 days. Subacute poisoning is more common and may result in death after 1 to 3 weeks of illness and weight loss. Raw photosensitized surface areas are susceptible to invasions by blowfly maggots and bacteria. In severely affected cattle, lesions may appear at the muzzle, mouth, and nostrils. Ulceration may be present in the cheeks, tongue, and gums, while swelling, hardening, peeling of mucous membranes, and deeper tissues occur in the nostrils.

Animals Affected

Cattle, sheep, horses, dogs, cats, guinea pigs, and rabbits

References Used

Ross, I. A. (1999). Medicinal plants of the world: Chemical constituents, traditional, and modern medicinal uses. Totowa, N.J.: Humana Press.

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/lantana

Lupinus (Lupine)

Description

Lupine is a herbaceous perennial, 12-26 inches tall. Leaves are alternate, palmately divided into 10-15 narrowly oblong leaflets. The leaflets are smooth or hairy above, and very hairy beneath. Bonnet-shaped flowers are born in racemes on a single center stalk 4-10 inches long. The flowers bloom in early to mid summer displaying their wide range of colors from deep blue, purple, light blue, lavender, rose, pink, yellow, and white. The fruit is a pod about one inch long containing several somewhat flattened seeds. The seeds are cream-colored and irregularly circular, and no more than 1/4 inch in diameter. 

Distribution

Lupines thrive in dry open fields and prairie/wooded areas. The horticultural variety of lupine has been a favorite of many gardeners for ages. Though Lupine in Illinois is most frequently seen in flower gardens, most of the approximately 100 native species are found throughout the U.S. and Canada, mainly in states west of the Rockies. A blue wild variety of lupine covers Texas open ranges in early summer, earning the rank of the State Flower. A different wild variety is also widely encountered in early summer by the visitors of the Olympic National Park in the State of Washington. 

Conditions of Poisoning 

Poisoning varies depending on the lupine species and varieties, and it is difficult to pin point to specific plant or animal since different animals become susceptible in different ways under varying range conditions.

Species and taxonomic differentiation between species are insufficiently characterized. Different lupines produce varying syndromes in a a given species of livestock. Seasonal variation in toxicity in a given species of lupine exist and many species are acceptable forage under range conditions. Plants which are in the preflowering stage of maturity are unlikely to be hazardous, under normal range circumstances, except in the case of L. leucophyllus which may cause toxicosis as a result of consumption of young plants. Alkaloids are not lost upon drying. Range hay may be highly toxic if the seeds are retained, and this occurs when the majority of the pods are immature; mature pods open when drying and the seeds are dropped as the hay is bundled. For many lupines, the time and degree of seeding varies year to year.

Most losses occur under conditions in which animals consume large amounts of pods in a brief period, such as trailing animals through an area where the grass is covered by snow but the lupine is not or when feeding podded lupine hay, which is apparently palatable. Most cases of serious poisoning therefore occur in the fall because lupine remains green after other forage has dried.

Toxic Principle

More than a dozen quinolizidine alkaloids, but some piperidine alkaloids and other types of alkaloids have also been isolated from species of Lupinus. These alkaloids are largely nicotinic in effect. The nitrogen oxides of some of these bases have also been detected in some lupines. The alkaloids are present in the foliage but the greatest concentration is in the seeds.

Clinical Signs

Signs include characteristic labored breathing (snores) in sheep, with depression, salivation, ataxa, clonic spasms, head pressing tremors, seizures and coma, and frequently death. Death may be preceded only by coma and no other signs or alternatively, preceded by violent attacks on other animals or objects. Signs may appear as early as one hour after ingestion or as late as 24 hours after consumption. Death may occur within one day or occur several days later and is a result of respiratory paralysis. Cattle under range conditions rarely display clinical signs. Consumption of the plant may also affect the flavor and odor of the milk produced by the poisoned animal.

Animals Affected

Sheep, cattle, horses

References Used

Knight, A. P., & Walter, R. G. (2001). A guide to plant poisoning of animals in North America. Jackson, Wyo.: Teton NewMedia.

M

Medicago sativa L. (Alfalfa)

Description

Alfalfa is an excellent forage crop when harvested and stored properly. However, the plant can cause "hepatogenous photosensitivity syndrome" if water-damaged (Monlux AW . J Am Vet Med Assoc, Vol. 142, 9, p. 989-994, 1963). 

Distribution

Alfalfa is commonly cultivated for animal feed, and instances of it growing in the wild often occur near areas where it is purposefully cultivated. Midwestern states where it is commonly found include Illinois, Tennessee, and Alabama, but it is also found in western states like Colorado and New Mexico.

Conditions of Poisoning 

Consuming fresh alfalfa can cause cause bloating in cattle and sheep. Additionally, "saponins found in alfalfa limit its use for swine and poultry." (Source: Cornell University Plants Poisonous to Livestock

Control 

Limit your livestock's intake of alfalfa, and ensure that you're not feeding them moldy or damp feed. 

Toxic Principle

All parts of the plant. The primary poisons are canavanine and saponins.

Clinical Signs

Fresh alfalfa can cause bloating in cows.

Animals Affected

Cattle, chickens, sheep, horses

References Used

http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:30234961-2#distribution-map