Dallas park officials will treat areas around White Rock Lake with an herbicide Friday after highly toxic hemlock was found growing near the water.

Maintenance crews with the parks and recreation department recently spotted “several populations” of water hemlock, a species of hemlock that grows in wet locations, along the lakefront, according to a draft news release.

Removing the plant is an “urgent priority” because of the risk that parkgoers might come into contact with it, city officials said. Dallas parks director John Jenkins said it was found in about half a dozen locations around the lake.

Hemlock is a highly toxic plant that grows to between about 1½ to 3 feet tall. The plant has small groups of white flowers in an umbrella formation, similar to a common yarrow or cow parsnip, the city said.

Hemlock acts on the central nervous system and is a “violent convulsant.” It is most toxic when ingested, but reactions can also occur after a person touches the plant. Symptoms can appear in as few as 10 minutes after contact, the city said.

The city’s urban biologist examined the areas where the plant is growing and found that hand-pulling or mowing the areas would present too great a risk to city employees and the public.

The herbicide Rodeo, also known as glyphosate, will be used instead. If it’s effective, the chemical will dry up the hemlock’s roots and neutralize its toxicity.

Maintenance crews will monitor the herbicide’s effectiveness and determine whether additional treatments are needed.

Park visitors should avoid touching the plant until the city fully eradicates it, the news release said.

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