Water hemlock

About

A native wetland plant in the carrot family and among the most violently poisonous plants in North America. A piece of root the size of a walnut can kill a cow or horse, and western water hemlock (Cicuta douglasii) is just as dangerous.

Also called spotted water hemlock, cowbane, spotted cowbane, beaver poison, western water hemlock

How to identify it

Look for

Hollow stems, often streaked or mottled purple, grow 2 to 8 feet tall and carry umbrella-shaped clusters of small white flowers. Leaves are divided two or three times into narrow, toothed leaflets, and the side veins run to the notches between the teeth, not to the tips. The thick base of the root is split inside into hollow chambers that ooze a brown or straw-colored poisonous liquid.

Look-alikes

It is easily mistaken for poison hemlock, wild parsnip, wild carrot (Queen Anne's lace) and edible wild herbs. Check for leaf veins that end in the notches and a chambered root base (wild carrot has densely hairy stems), and never eat any wild carrot-family plant.

Where it grows

Wet ground: stream and pond banks, marshes, wet meadows, wet pastures and ditches.

When

One of the first plants up in spring; flowers from late spring through summer, and seed forms later in summer.

How it spreads

Spreads by seed, which can stay alive in the soil for a few years, and regrows each year from its root clusters.

Most common in

What to do, gentlest first

Protect yourself first. Weed killers are a last step; always read and follow the label.

1. Know it and fence animals out Prevent

   Learn to recognize it before working in wet spots. Keep livestock out of wet areas where it grows, especially in spring, and wear gloves when handling it.

   Take care not to expose or scatter roots when cleaning ditches or clearing land.

2. Dig out the whole plant in moist soil By hand

   When the soil is moist, pull or dig out the entire plant, including every root, while patches are still small.

   Wear rubber gloves and bag everything for the trash. Never burn it. Wash gloves and tools afterward.

3. Spot-treat young plants with 2,4-D or glyphosate Conventional spray

   Treat young plants in late spring or early summer. Repeat in later years, and keep animals away from treated plants for about three weeks.

   Read and follow the label. Many lawn and brush herbicides also kill garden plants, so keep spray and drift off anything you want to keep. Within about 50 feet of water, use only products labeled for aquatic use.

Uses, wildlife and pets

For wildlife

Bees, wasps, butterflies and moths visit the flowers, and it is a host plant for black swallowtail caterpillars.

Pets

Toxic to dogs, cats and horses (ASPCA); signs include seizures, tremors, severe belly pain and breathing trouble, and it can kill.