Spotted water hemlock, a native North Dakota plant, has been reported in most North Dakota counties. The plant is highly poisonous to humans and all livestock, especially cows, horses and goats. The plant's toxin, cicutoxin, is most harmful in the spring. The roots are the most toxic, but all parts of the plant can be poisonous.

Spotted water hemlock is a short-lived perennial plant that spreads by seeds and roots, and thrives in moist to wet soils, allowing floodwater and birds to help spread seeds. It is most often found in wet and subirrigated meadows and along the edge of cattail sloughs and low-lying roadside ditches, water drains and creek bottoms. However, it can occasionally be found in better-drained soils near these wet areas.

“Most cases of concern are when spotted water hemlock ends up in hay bales,” says Joe Ikley, NDSU Extension weed specialist. “Awareness and prevention are key. Avoid baling any plants you can’t confidently identify.”

With the much drier weather this year and the need to cut more acres of hay, NDSU Extension cropping systems specialist Jeff Stachler advises farmers and ranchers to scout wet areas for the presence of spotted water hemlock before cutting for hay.

A member of the carrot family, spotted water hemlock can be difficult to identify. It is often confused with water parsnip, a non-toxic native plant. Both grow in similar, moist-to-wet environments and can reach 2 to 6 feet tall. Most other carrot family species live in more well-drained soils.

Some distinguishing characteristics between spotted water hemlock and water parsnip include:

• Stem: Spotted water hemlock has smooth, reddish to purple streaked/vertical-veined hollow stems with chambered roots. Water parsnip has green, somewhat angled stems with little to no hair, and a nearly square stem at the base of the compound umbel.
• Leaves: Spotted water hemlock leaves have one to three subdivided leaflets with a more deeply toothed leaflet margin. Water parsnip leaves have paired single leaflets with short, sharp margins and are not subdivided like spotted water hemlock.
• Flowers: Spotted water hemlock has compound umbel flower heads in more of a dome shape, about 4-6 inches across, while water parsnip has compound umbel flower heads that are flatter and smaller, about 2–5 inches across.

“The plant’s sap may cause skin irritation in some people,” says Ikley. “Use caution and wear gloves when investigating unknown plants.”

Kevin Sedivec, NDSU Extension rangeland management specialist, says that livestock typically avoid the plant unless other forage is limited, as it is becoming this year in the southwest, southern and eastern parts of North Dakota. When dry pastures push cattle into wetter areas to feed, animals may pull up younger plants and may consume the roots, which are the most poisonous.

“Problems are most likely to arise when the plant is unknowingly cut and included in hay,” Sedivec says. “If you know the plant is in your meadow or road ditch, it’s safest to mow around it.”

If hay containing spotted water hemlock has already been harvested, Extension specialists advise feeding it in a way that allows livestock to pick through it, such as in bale feeders or as roll-out hay, rather than mixing it into ground rations, which prevents animals from avoiding the toxic material. Livestock should not be forced to clean up uneaten hay containing spotted water hemlock.

The best management is to identify where spotted water hemlock is located and avoid cutting for hay. If forage is plentiful, cows and horses can have access to these areas, as spotted water hemlock is not a preferred plant; however, if forage becomes limited, they will graze this plant, increasing the risk of poisoning. Sheep and goats prefer forbs and wildflowers and may select for the spotted water hemlock.

If the area becomes dry, mowing spotted water hemlock plants as soon as possible with a rotary mower will reduce seed production and future seed spread.

“Application of aquatically approved 2,4-D ester formulations in the fall after a light frost is the best way to manage spotted water hemlock with herbicides,” says Stachler.

Aquatic glyphosate formulations applied in the fall can effectively control spotted water hemlock, but will also harm or kill nearly all desirable herbaceous plants. For plants growing near water, always apply herbicide products labeled for aquatic areas; however, if water is definitely not present, apply non-aquatic formulations of these herbicides.

“Remember, 2,4-D ester and glyphosate will control all desirable wildflowers in the meadows, so choose wisely,” Stachler says. “Always read and follow label directions.”

Regular scouting and long-term management through rotary mowing to reduce seed production will help reduce establishment in unwanted areas.

For assistance with identification of spotted water hemlock, contact your county NDSU Extension office at ndsu.ag/countyoffice.

NDSU Agriculture Communication – July 27, 2026

Source: Jeff Stachler, 701-652-2951, jeff.stachler@ndsu.edu

Source: Joe Ikley, 701-231-8157, joseph.ikley@ndsu.edu

Source: Kevin Sedivec, 701-424-3606, kevin.sedivec@ndsu.edu

Editor: Elizabeth Cronin, 701-231-7006, elizabeth.cronin@ndsu.edu