In the Pacific Northwest, there are many poisonous plants. This creates problems for many gardeners, farmers, or even pet owners. There is a saying that goes something like ‘Leaves in threes, let it stay!’ which is not always accurate. A lot of poisonous plants look alike, even if they have completely different effects on the human body.
One is giant hogweed, Heracleum mantegazzianum, that looks like dandelions without the bottom part of the dandelion, with others sprouting from the trunk of the stem. The size of a giant hogweed is distressing, fourteen feet high, with two to four inches in diameter. Giant hogweed can cause blisters, rashes, and even blindness, because it gives skin more of a sensitivity to the sun. Giant hogweed is usually found in western Washington.
Another terrible breed of plant is hemlock. Both poison hemlock, western water hemlock, and water spot hemlock are poisonous to humans. Both types of hemlock have tiny flowers that come off of the thick stem of the plant and small zigzaggy leaves. Poison hemlock, Conium maculatum, is lethal even with small doses, but can also result in numbness, skin irritation, vomiting, drowsiness, and more. Spotted water hemlock, Cicuta maculata, looks the same other than the longer leaves, but causes abdominal pain, seizures, nausea, and convulsions. Ingesting spotted water hemlock can lead to death. The western water hemlock, Cicuta douglasii, are related to carrots and the flowers are yellow and white, and the stem purplish brown. If eaten, the western water hemlock can cause rapid breathing, convulsions, along with comas and death. Poison hemlock grows near moist areas, spotted water hemlock grows all over north america, and western water hemlock thrives in meadows and wetlands.
Cow parsnip, Heracleum maximum, has a sticky stem with a lump before the smaller flower stems come. On the flower stems there are tiny flowers that resemble moths with their wings tucked in. Their leaves are similar to maple leaves in shape, but with the center of the leaves sinking. Cow parsnip can cause blisters, skin discoloration, burns, and rashes. Another type of parsnip, wild parsnip or Pastinaca sativa, has vibrant yellow flowers and thicker leaves. Wild parsnip isn’t exactly poisonous, but the state of Washington advises people not to touch it since its sap, similar but less bad that giant hogweed, can cause skin irritation and blistering rashes, along with being around five feet tall.
In conclusion, there are many plants in Washington that are poisonous, including giant hogweed, poison hemlock, western water hemlock, spotted water hemlock, cow parsnip, and wild parsnip that look similar to each other (and I didn’t even talk about poisonous mushrooms or foxglove).
Works Cited
“Don’t touch these plants! | U.S. Fish & Wildlife Service.” U.S. Fish and Wildlife Service, https://www.fws.gov/story/dont-touch-these-plants. Accessed 23 April 2026.
This is an article about plants in Washington that are dangerous to touch or ingest. This source has a lot of information about what the plants can do and why they cause reactions. This article does not say when it was published. This article was published in the U.S. & Wildlife Services website, which is a government website. There should not be any bias on this article.
Glatz, Kyle. “Beware: These 10 Plants in Washington State Can Harm You.” A-Z Animals, 11 May 2023, https://a-z-animals.com/blog/beware-these-10-plants-in-washington-state-can-harm-you/. Accessed 23 April 2026
This is a list of poisonous plants in Washington. This source has a lot of information about where in Washington you find these plants and what they do to the human body. This was published on June 29, 2023. This article was published on A Z Animals. There should not be bias on this article.