Water hemlock is a common poisonous native plant


Ted Manzer

Friday, July 27, 2018

We’ve all heard the story of how Socrates was forced to drink a potion containing poison hemlock. All parts of it are toxic, and the plant is relatively common in many places, including this region. Plants are deathly poisonous to livestock, pets and humans.

We have another lookalike to this toxic weed. Not only does water hemlock look like poison hemlock, it’s even more common and more toxic. All parts of the plant can kill you in as little as 15 minutes. According to several sources, it only takes a piece of root the size of a walnut to kill a 1,200-pound cow or horse.

Both species strongly resemble Queen Anne’s Lace, often called wild carrot. Wild carrot is a commonly used medicinal plant and is often found near the poison imposters. All are in the same plant family, as is wild parsnip, a common foraging herb. It can be confused with its poisonous relatives also.

Water hemlock, like the name implies, is usually found in wet places. Many ditches are full of it. It’s blooming right now as are most of its nonpoisonous cousins. Plants are usually three to six feet tall, but I’ve seen some significantly taller.

Flowers grow in white circular clusters called umbels. Several small umbels make up a larger disc-shaped structure called an inflorescence. Leaves emerge from stems one at a time. They are what botanists call tri-pinnate, in that they branch three times and individual blades run three directions. Blades have toothed edges.

Most folks need not worry too much about water hemlock, since it generally grows in wet places they do not frequent. However, their pets might romp in thick patches of it. Furthermore, seed can be dispersed into places where livestock might consume it.

Killing it can be a little tricky. I’ve read where a combination of glyphosate and imazapyr can be effective. Both are non-selective, which means they kill whatever they hit. Both are also systemic. That means they kill the entire plant.

Finding herbicides that will kill water hemlock only solves one part of the problem. There are regulations concerning spraying pesticides in waterways. Contacting someone who knows the regulations is important or you might wind up in trouble.

There are guidelines that must be followed before spraying pesticides in or near water, particularly if there is risk to drinking water supplies or a neighbor’s property. Sometimes hiring a professional with proper licensing and liability insurance is a wise move.

Another problem with spraying water hemlock is that while plants are dying, palatability for livestock increases. Keeping pets and livestock from accessing treated areas is critical.

Now that I’ve thoroughly scared you, water hemlock is still used as a medicinal herb. Preparations can be made to control migraines, menstrual pain and intestinal worms. I wouldn’t recommend this to anyone under any conditions. Much safer options are available.

If I offend any herbalists out there, I’m sorry. Using water hemlock to treat any human or livestock ailments is insane. Even the slightest dosage miscalculation could be fatal.

Ted Manzer teaches agriculture at Northeastern High School.