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Watch for these 3 toxic range plants

OlyaSolodenko/Getty Images Hemlock flowers
WATCH OUT: Water hemlock is one of the plants that can be toxic and potentially deadly to cattle and other livestock when ingested.
Learn how to avoid hemlock, halogeton and buffalo bur in your pastureland.

Hemlocks, halogeton and buffalo bur are poisonous plants that South Dakota State University Extension has seen in various areas of pasture and rangeland. Several species of poisonous plants are invasive and can easily establish dense stands when there is a disturbance on rangelands.

Here is more information on the three plants that are found throughout South Dakota and are toxic to livestock:

Hemlock. A member of the carrot family, this biennial is characterized by having small leaves with five petals and compound umbels. Water and poison hemlock are the two species found throughout rangelands in South Dakota. Both are extremely poisonous to livestock and humans alike, making proper identification crucial.

Water hemlock (also known as spotted water hemlock) has alternate, bi-or tri-pinnate leaves that are 4.5 inches in maximum length and strongly veined with serrated edges. The plant has large, green, hollow stems, with the lower portion being purplish, and an umbel inflorescence that looks like an umbrella composed of tiny five-petaled, white flowers. Water hemlock is found across South Dakota in water-filled sites, such as riparian areas, wet meadows, and ditches or springs.

Poison hemlock (also known as deadly hemlock) prefers drier, disturbed sites, including pens and manure piles, cultivated fields and gardens, ditches and fence lines, or wet areas that dry up in late summer.

Although it can sporadically be found across South Dakota, poison hemlock is commonly found throughout the Black Hills region. It is identified by large, compound leaves that resemble parsley and hollow, pale-green stems with purple spots, and a flattened, white umbel inflorescence.

Poisoning from hemlocks is caused by ingestion of any part of the plant, especially the roots, seeds, young leaves and new shoots, due to harmful alkaloid compounds. Livestock will generally not graze hemlocks if adequate forage is available.

Symptoms of hemlock poisoning include:

  • trembling
  • loss of coordination
  • dilated pupils
  • weakened heartbeat
  • sudden death caused by respiratory failure

There is no treatment or cure for hemlock poisoning, as effects are often rapidly fatal. Water hemlock is regarded as the most violently poisonous plant in North America.

Both species of hemlock have commonly been mistaken for wild parsnip and caused poisoning in humans.

Halogeton. This plant has small, alternate, bluish-green leaves that are succulent-like with a short bristle at the end and curved, reddish-pink stems that branch from the base of the plant. When halogeton flowers, very small greenish-yellow sepals become present with the highly visible bright reddish-pink stem attachments across the entire plant.

Halogeton is reported to be an invasive plant in Badlands National Park in South Dakota and can be found elsewhere throughout the southwestern part of the state. Arid regions with alkaline soils and disturbed sites are the most-common ecosystems where halogeton will thrive.

Halogeton accumulates salts, including toxic amounts of sodium oxalates that make it fatal to livestock, especially sheep. Livestock will readily graze the plant when it is mature.

Symptoms of livestock poisoning from halogeton will appear two to six hours after ingestion and will include:

  • weakness
  • shallow breathing
  • coma
  • death from kidney failure

Proper control of halogeton is critical but is also difficult, as each plant produces large numbers of seed that can survive in the soil for 10 years or more. Plants can be controlled with proper use of herbicides, with small infestations eradicated if treated early. Specifically, 2,4-D will kill over 95% when applied in late May or early June, but it is not selective.

Instead, several steps can be taken to prevent halogeton poisoning, such as maintaining rangelands that support adequate forage, providing supplemental feed when animals trail or graze through an infested area, and preventing animals from becoming hungry or thirsty while grazing areas that are infested with halogeton, as they graze indiscriminately.

Buffalo bur. Also known as prickly nightshade, this plant has many bright-yellow, five-petaled flowers that blossom all summer, along with spiny thorns covering the plant and deep-green, alternate, round-lobed leaves. The plant has “burs” that are covered in spines and contain a berry.

Buffalo bur is found across South Dakota in disturbed areas, such as ditches, cultivated lands, feedlots, depleted rangelands and on sandy sites, including river bottoms. It is a very drought-tolerant plant and is seen in abundant stands during dry years.

Like other members of the nightshade family, buffalo bur contains toxic alkaloids. If the leaves or berries are ingested, a dose as small as 0.1% to 0.3% of body weight can be lethal for cattle. Sheep and goats are less susceptible to be poisoned by the plant. Livestock are generally discouraged to eat buffalo bur due to its spiny thorns; however, producers should be cautious of grazing an area if it is abundant and the only plant available to be grazed.

Find identifying photos of these and more invasive plants at SDSU Extension.

Source: South Dakota State University Extension, which is responsible for the information provided and is wholly owned by the source. Informa Business Media and its subsidiaries aren't responsible for any of the content contained in this information asset.


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