08.18.07
Poisonous Cowbane Is Ongoing Concern in Gilford
Spotted Water Hemlock (cicuta maculata aka. Cowbane,) a plant highly toxic to livestock and people if ingested, is still a growing threat in areas of Gilford. As reported last summer, owners of grazing animals should beware, especially if Cowbane is found near drinking water sources. The roots if trampled can poison a small pond with a deadly neurotoxin which can kill animals drinking it.
Toxic effects
Identified three and five years ago on Schoolhouse Hill Road and Watson Road by county and state agents, and verified last summer by the New Hampshire Department of Agriculture, this season’s stands of Cowbane are not as lush as last summer which saw an excess of rain. Nevertheless, it is still present and spreading. It is considered one of the most poisonous plants in the U.S., containing a deadly toxin which affects the central nervous system when ingested. The roots of the Water Hemlock have a high concentration of cicutoxin, lethal even in small amounts. One gram of Water Hemlock per kilogram of body weight will kill a sheep, and eight ounces (approximately 230 grams) is enough to kill a horse.
Fresh leaves and stems can also be deadly when browsed in the spring. Roots getting into a haycrop are a real danger, since drying does NOT reduce the toxicity of the roots. Animals have been poisoned by drinking water contaminated by trampled Water Hemlock roots. Humans have died after only one or two bites of root, mistaken for wild parsnip or artichoke.
How to identify
Related to the parsnip, carrot and parsley family, Cowbane can grow up to 6 feet tall when flowering, with stems up to two inches thick at base; it produces white blooms similar in appearance to Queen Anne’s lace in late summer, and is easiest to spot right now while in bloom. It has leafy lower foliage and thick, often purplish-striped or mottled, hollow jointed stems somewhat like bamboo; broken stems may exude yellowish oily or watery liquid smelling like parsnip. Cowbane is biannual– first-year plants will be lower to the ground and leafy; they bloom in their second year, when the tall thick flowering stem spikes are sent up.
Known locations in Gilford
Cowbane grows in damp, marshy areas, and recent rainy summers have helped its spread locally, often along stream banks and roadside drainage ditches. Stands of Water Hemlock/Cowbane have been identified in the following locations in Gilford (and may be in other areas as well):
Schoolhouse Hill Road
Gunstock Hill Road
Watson Road
Gilman Road
Old Lake Shore Road
Cherry Valley Road at 11B junction and along Gunstock stream
Henderson Road in the stream under the bridge
How to control
In controlling the Cowbane’s spread, precautions should be taken, according to Doug Cygan, N.H. Dept. of Agriculture (contact info below):
Wear rubber gloves, and avoid skin contact with sap, especially to face or eyes– when it’s flowering, there is also chance of a dermal (skin) reaction to the pollen or even an asthmatic response;
Use spade or tined fork to uproot the plant and remove its branching root system;
Place plants in black plastic trash bags, out of reach of pets;
Place bags in the sun to “cook” for a few days to dry out the plants;
They may then be disposed of in regular trash.
As concerned horse owners, my husband and I, along with several of our neighbors, have for two years mowed down large patches of Water Hemlock and also pulled up individual plants. Because it is a biannual, frequent mowing every year is effective; mowing just as it starts to flower would limit new outbreaks. Spraying with an herbicide suitable for woody-stemmed plants such as poison ivy should kill it. We urge other area residents to help curtail the spread of this dangerous species immediately, while it is easiest to identify and before full bloom has seeded new plants.
To find more information and photographs of poisonous Spotted Water Hemlock online:
Purdue– toxic plants
All Creatures
Survival IQ
NCSU Horticulture Dept.
CT. Botanical Society
My report here last year…
Please note that Emails, calls or letters of concern are encouraged by the state, to help focus attention onto this New Hampshire problem.
Doug Cygan 603-271-2561
Division of Plant Industry
Invasive Species Coordinator
NH Dept. of Agriculture, Markets & Food
P.O Box 2042
Concord, NH 03302-2042
NH Dept. of Agriculture, Markets & Food
State House Annex
25 Capitol Street, 2nd floor
Concord NH 03301
Email: dcygan@agr.state.nh.us
Website– general info, invasive plant species list, etc.: NH Dept. of Agriculture
