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Waterhemlock Reported in Cass County (07/21/21)

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I have received a couple questions and ID samples for spotted waterhemlock over the last two weeks. Spotted waterhemlock (Cicuta maculata) is one of the most acutely poisonous plants we have in North Dakota. The reported infestations have been in grass hayland adjacent to dried up cattail sloughs, adjacent roadside ditches and water drains. It is probable that these plants were established several years ago and have since spread. Waterhemlock spreads by seed and thrives in moist soils, so floodwaters are of great concern in aiding the spread of waterhemlock.

Spotted waterhemlock is a perennial weed in the parsley family. It can be easily confused with other plants in this family due to the flowering structures. Spotted waterhemlock has clusters of white flowers arranged in an umbel, similar to other weeds like wild carrot or poison-hemlock. The leaves of spotted waterhemlock can help differentiate it from similar species. Spotted waterhemlock leaves are narrow-toothed, 1-4 inches long, and divided 1-3 times. The leaflet veins run from the midrib to the tips of the leaf margins. Another identifying characteristic is a hollow stem that often contains hollow, horizontal chambers that can be observed by splitting the root base of the plant. Use caution when splitting a root, as this is the most toxic part of the plant and can cause skin rashes on some individuals.

Spotted waterhemlock is a weed of great concern to livestock producers due to its toxicity when ingested. Typically, ingestion will take place when spotted waterhemlock is mixed in with hay bales. Any potential plants should be mowed around to avoid baling, and care should be taken to avoid feeding at all costs. Other states have reported that chemical control is best achieved with high rates of glyphosate, 2,4-D, or MCPA at the bud-to-early-bloom stage. The infestations that were walked are all past that growth stage, so the level of control using these products is not known, but will likely be less than earlier applications. If plants are in or near water, then formulations that are safe to apply in aquatic settings should be used. Livestock producers should be on the lookout for this weed and long-term management will be needed to control these infestations and prevent accidental ingestion by livestock.

Spotted waterhemlock in a ditch with cattail
Photo Credit:
Stan Wolf
Close up of leaves of spotted waterhemlock. Note veins that spread from midrib to toothed margin of leaves and Hollow horizontal chamber found in root of spotted waterhemlock.
Photo Credit:
Stan Wolf

 

Joe Ikley

Extension Weed Specialist