How much sun does Western water hemlock need?

Western water hemlock grows best in full sun conditions.

When does Western water hemlock bloom?

Western water hemlock blooms in June, July, and August.

Where is Western water hemlock native?

Western water hemlock (Cicuta douglasii) is native to CA, ID, MT, NV and 3 more states, per the World Checklist of Vascular Plants (Kew).

Is Western water hemlock toxic to dogs?

Yes. Western water hemlock is listed as toxic to dogs by the ASPCA Animal Poison Control Center (aspca.org). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.

Is Western water hemlock toxic to cats?

Yes. Western water hemlock is listed as toxic to cats by the ASPCA Animal Poison Control Center (aspca.org). If your cat has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.

What pollinators does Western water hemlock attract?

Western water hemlock draws flies, small bees, and beetles.

Western water hemlock

Name: Pollinator Patch
Author: Pollinator Patch

Cicuta douglasii

Last reviewed: September 2026

Western water hemlock (Cicuta douglasii) is a perennial forb native to CA, ID, MT, NV and 3 more states. It blooms in June, July, and August. The flowers draw flies, small bees, and beetles.

Western water hemlock is toxic to dogs and cats.

Listed as toxic by the ASPCA Animal Poison Control Center (opens in new tab) (last reviewed 2026-08-15). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435 and your veterinarian's emergency line.

Pollinator Patch flags toxic plants so you can choose a pet-safe native alternative for your yard.

Light

full sun

Water

high

Size

24"–72" H × 18"–36" W

Bloom

Jun, Jul, Aug

Native to

CA, ID, MT, NV and 3 more states

Pollinators

flies, small bees, beetles

Before you buy

Your city may pay you to plant this

Cities and water utilities offer rebates for replacing lawn with native and water-wise plants. We track 458 programs across 44 states, each with a link to the provider and the date we last checked it.

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Browse plants for this ecoregion

Coast Range Puget Lowland Marine West Coast Forest Northwestern Forested Mountains Sierra Nevada Central California Foothills and Coastal Mountains Southern California Mountains North American Deserts Central Basin and Range Southern Rockies High Plains

A tall wetland perennial with hollow stems and compound leaves, topped by flat clusters of small white flowers, found along streambanks and marshes. All parts of the plant are highly toxic if ingested.

Growing Western water hemlock

Grow Western water hemlock in full sun and high water. Mature plants reach 24 to 72 inches tall and spread 18 to 36 inches wide.

Wildlife value

The flat flower clusters attract a wide range of small pollinating insects, though the plant poses a serious poisoning risk to people and livestock.

Common questions

How much sun does Western water hemlock need?: Western water hemlock grows best in full sun conditions.
When does Western water hemlock bloom?: Western water hemlock blooms in June, July, and August.
Where is Western water hemlock native?: Western water hemlock (Cicuta douglasii) is native to CA, ID, MT, NV and 3 more states, per the World Checklist of Vascular Plants (Kew).
Is Western water hemlock toxic to dogs?: Yes. Western water hemlock is listed as toxic to dogs by the ASPCA Animal Poison Control Center (aspca.org). If your pet has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.
Is Western water hemlock toxic to cats?: Yes. Western water hemlock is listed as toxic to cats by the ASPCA Animal Poison Control Center (aspca.org). If your cat has been exposed, call the ASPCA Animal Poison Control Center at (888) 426-4435.
What pollinators does Western water hemlock attract?: Western water hemlock draws flies, small bees, and beetles.

Native range data from the World Checklist of Vascular Plants (Kew). Pollinator and host plant associations compiled from GBIF, iNaturalist, and published ecological literature.

If something looks wrong

Common plant problems, and what to check first

These come up on almost any plant. Each guide lists the likely causes in the order they are worth ruling out, with one thing to check before you act on any of them, and links to the source it came from.

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