Scientific name: Conium Maculatum

What Is It?

Poison hemlock is an acutely toxic plant that, if ingested, can kill humans and animals within a few hours. It may be found in a wide range of areas including fields, roadsides, gardens, and trails or in drier parts of the state, near ditches or other sources of water. It is a prolific seeder and is spread through animals, water, erosion, and human activity.

Is Is Here Yet?

Yes. It is found across the country and throughout the entire state.

Why Should I Care?

Poison hemlock may be easily confused with similar-looking edible plants, like carrots, wild parsnips, parsley, or anise. A few hundred grams of leaves can kill. Poison hemlock also can be toxic through contact with the skin, or through inhaling when mowing through large parches of the plant. All parts of the plant are poisonous and even the dead canes remain toxic for up to 3 years. Call a veterinary clinic or poison control center (800-222-1222) immediately if you suspect an animal has ingested poison hemlock.

How Can We Stop It?

Poison hemlock may be controlled by pulling or digging out the plant, including the entire taproot. Wear gloves before handling the plant, as every part of the plant is toxic. Mowing is less effective, as plants can regrow quickly. Throw poison hemlock plants in the garbage, not in yard waste. Plants are still poisonous when they are dry.

What Are Its Characteristics?

  • Herbaceous, meaning it lacks a woody stem, but can grow up to 12 feet tall.
  • Feathery, fern-like leaves with a strong, musty smell.
  • Stem is hollow and green with red-purple spots or splotches, and not noticeably hairy.
  • Small white flowers grow in flat-topped umbrella-like clusters at ends of stems.
  • Biennial with low-growing plants visible most of the first year, and taller plants the second year that bloom in May and June.
  • Produces up to 40,000 seeds per plant that germinate throughout the growing season.

How Do I Distinguish it From Native Species?

As a member of the carrot family, it looks very similar to many other members of that family. The native species, water hemlock, looks similar, but is only 3-6 feet tall, doesn’t have such lacy leaves, and grows almost always in wet areas and shorelines. Although native, water hemlock is even more toxic than poison hemlock and should never be consumed. Other plants that are similar to poison hemlock don’t have hairless, purple-spotted stems or are much shorter than poison hemlock. Wild carrot or Queen Anne’s lace, for instance, has hairy stems and doesn’t get as tall. Water parsley is also much shorter, doesn’t grow as upright, and lacks purple spots on the stems.

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