Poison hemlock has begun to bloom. The white flowering plants are easily visible along roadsides, edges of fields, stream banks, fence rows, and other unmowed areas. The flower stalks are quite impressive, being 3 to 8 feet tall.
I first introduced this weed to readers last year, but it is important to discuss again because of its toxicity to livestock and people.
All parts of the plant are poisonous and may harm animals and people if enough is consumed.
Fortunately, most livestock will not eat the leaves of poison hemlock when other feed and plant sources are available in a pasture.
The toxin is present even in dried plants, so contaminated hay is still a concern. Portions of hayfields or other potential forage areas infested with poison hemlock should not be harvested.
People may be poisoned by eating any part of poison hemlock. Poisoning cases have often occurred when a person confuses poison hemlock roots for wild parsnip, leaves for parsley, and seed for anise.
Children have died from playing with whistles made from the hollow stems of poison hemlock.
Illness may also occur from absorbing the toxin through the skin and breathing the plant dust, so wear protective clothing such as gloves, goggles and masks when handling this plant.
Poison hemlock is an exotic plant native to Europe and Asia. It was introduced into our country as an ornamental plant, which escaped and became an invasive plant across northwestern Ohio.
Clusters of tiny white flowers are borne on structures called umbels, because they look like upside-down umbrellas, on the upper part of the flowering stalks. Flowering season will last through August.
Poison hemlock, Conium maculatum, tends to live for two years. It grows as a basal rosette the first year and, in the second year, it will bolt and produce a towering flower stalk. However, it may act like a short-lived perennial under optimal conditions.
It is a member of the carrot family, so it shares many characteristics with other weeds found in Ohio, including native wild carrot, also called Queen Anne’s Lace, Daucus carota, and wild parsnip, Pastinaca sativa, a non-native plant.
Wild parsnip has yellow flowers, and wild hemlock and wild carrot both have white flowers. Poison hemlock may be distinguished from wild carrot flowers by looking at the stem.
Poison hemlock has purple spots or blotches and no hairs along the flower stem. Wild carrot has no blotches and is usually covered with hair.
All growth stages of poison hemlock have bluish-green leaves that are fern-like, and the deeply cut parsley-like leaflets have sharp points. Wild carrot has more rounded than sharp points.
Poison hemlock spreads by seed. The dried fruit is easily moved to new areas by wind, birds and rodents.
Control methods include manual removal, mowing, tilling, or herbicides. It is best to control while in the rosette stage, particularly in the fall.
Manual removal, including the roots, is practical when only a few plants are present in an area. Do not compost removed plants, but place in plastic trash bags and dispose with other trash.
Do not take plants to municipal yard waste disposal sites, and make sure to remove plants before seed dispersal. Also wear protective clothing, gloves and dust mask while handling.
Mowing or cutting with a weed-trimmer before flowering can be effective. Wear a dust mask to avoid inhaling toxins while mowing or cutting.
For herbicide control, plants should be treated in the fall, but spring application will be effective prior to flowering.
Triclopyr, 2,4-D plus dicamba, and metsulfuron are effective herbicides that will not kill grass around hemlock. Glyphosate (Roundup) may be used as a non-selective herbicide. Herbicide applications may need to be repeated for full control.
Be careful when working around poison hemlock. Pictures and additional information may found at http://www.oardc.ohio-state.edu/weedguide/singlerecord.asp?id=550 and http://www.btny.purdue.edu/weedscience/2003/articles/PHemlock03.pdf.
Separately, farmers will finish adding nitrogen to corn in multi-application systems. Some farmers still have some soybean acres to plant or replant. Wheat is now in the grain-fill stages.
Lentz is extension educator for agriculture and natural resources for The Ohio State University Extension Service in Hancock County. He can be reached at 419-422-3851 or via email at firstname.lastname@example.org.
Lentz can be heard with Vaun Wickerham on weekdays at 6:35 a.m. on WFIN, at 5:43 a.m. on WKXA-FM, and at 5:28 a.m. at 106.3 The Fox.
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