Last week I got a call from a lady who had weeds growing in her backyard that she couldn’t identify. Her neighbors told her it was dangerous and that she should burn it. She wanted to contact Extension before doing anything.
I wanted to see for myself what it was. I had a suspicion after she told me it had white flower clusters and that she lived by the river. I drove to the Lakeshore area where her backyard was on the water. The view was beautiful and I saw a bald eagle fly overhead as I walked through the property. Then I saw the beautiful white flower clusters rising above the various grasses and forbes that made up her garden. I was concerned that she might have a stand of water hemlock (Cicuta maculata), but I still wasn’t sure. I looked closer and saw that the stems had purple stripes and the leaves were arranged alternately along the stem. I brought my gloves and pruning shears to cut into a stem. It was hollow inside. That’s when I knew the water was hemlock.
What is the most poisonous part of water hemlock?
Water hemlock is one of the deadliest plants in the world. It is a cousin of the poison hemlock that did that in Socrates. All parts of the plant are poisonous and contain a chemical called cicutoxin. Within 30-60 minutes of ingestion, a person will experience nausea, vomiting, tremors, cramps and convulsions. The most poisonous part of the plant is the root. In 1992, a 23-year-old man and his brother were looking for wild ginseng root in Maine. He accidentally collected and ate 3 bites of water hemlock root. Despite emergency services arriving within 30 minutes and receiving aggressive treatment at a hospital, he succumbed within three hours. The older brother, who took only one bite, was treated and survived.
What other plants look like water hemlock?
According to CDC data, at least 58 people died between 1979 and 1988 after ingesting a misidentified poisonous plant. There are a few plants that look a lot like water hemlock. One of these is Queen Anne’s lace (Daucus carota). This plant belongs to the carrot family and grows like a wildflower, although it is not native to the United States. All parts of the plant are edible, both cooked and raw. Flower clusters can be fried and have a carrot-like flavor. The stems are hairy and the flower clusters have a dark purple bloom in the center.
Another look-alike is elderberry. People often collect the fruit for use in pies and jams. It also grows on the banks of lakes and ponds and has white flower clusters. However, the inside of the stem is spicy and the leaves lie opposite each other along the stem.
Where is water hemlock found?
I contacted a cannabis scientist and a botanist from the University of Florida to help me advise the lady. The cannabis scientist told me that complete eradication of this plant would be virtually impossible and that the strategy might be to simply leave it alone. The plant is not harmful unless a person or animal eats it. The botanist agreed, noting that water hemlock is native to Florida and grew in its natural habitat along the river.
It serves as a host plant for the black swallowtail butterfly and provides nectar for numerous pollinators. It is true that as I walked past the hemlock I noticed a lot of bee activity and I also saw caterpillars on one of the plants. My client has a dog, but she walks the dog on a leash in the front yard, away from the plants. Although there are numerous reports of people and livestock being poisoned by water hemlock, no cases involving dogs have been reported. I reassured my client that it did not look like poison ivy and that touching it would not hurt. To prevent the disease from spreading, you can mow the affected area very close to the ground. Repeated mowing will reduce the plant’s ability to compete with other plants in the area. Spot treatments with herbicides can also be applied to control the plant. Systemic herbicides that penetrate all plant parts, such as glyphosate or 2,4-D, work best when applied in late spring and early summer. Plants growing in wet or submerged areas should be treated with an herbicide specifically labeled for use in wetlands, if treatment is even necessary.
Our native water hemlock provides nectar for pollinators and food for butterfly caterpillars. As long as it is not eaten, it poses no risk to people or pets. Florida has many other plants that are often purposely grown in our landscape that are also very poisonous. Sago palm, oleander and angel’s trumpet are the three top of mind. So you can love and live with a poisonous plant if you are careful.
Tonya Ashworth is an Extension Agent and Environmental Horticulture and Master Gardener Coordinator at UF/IFAS of Duval County.
This article originally appeared in the Florida Times-Union: Water hemlock is poisonous. Here’s what you need to know about it
