Last month, Aspinwall officials got a report from a resident that they didn’t quite know what to do with: a patch of poison hemlock was growing in the borough’s Fireman’s Memorial Park, on a walking trail next to a playground.

“We were surprised and confused,” said Aspinwall borough manager Melissa O’Malley. “We’ve had that park for over 50 years and we’ve never had to deal with it.”

Poison hemlock is a highly toxic plant in the carrot family that can grow up to 12 feet tall. If any part of the plant is ingested, it can cause dizziness, paralysis and even death from respiratory failure. Touching the plant causes a rash in some people, and inhaling particles from the plant or having sap from the plant come in contact with cuts can also be dangerous.

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The plant is a biennial, meaning that it takes two years to complete its life cycle. In year one, poison hemlock grows as a small rosette, just leaves close to the ground in a circular pattern. In year two, a thick stem with distinctive purple blotches shoots up, and the plant flowers and drops seed. A single plant can produce more than 30,000 seeds, which can stay in the soil for years. The best time to control the plant with an herbicide is in its first year or early in the second year. By the time it shoots up in year two, controlling it chemically is ineffectual.