Poison hemlock continues to be a problem weed in the area. It is commonly seen along roadsides, edges of fields, stream banks, fence rows, and non-mowed areas. At flowering, the plants are quite visible since they may reach heights of six to eight feet. The weed is currently flowering in the area.
All parts of the plant (leaves, stems, roots, and fruits) 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.
However, toxins will still be present if plants are harvested and dried in hay. Thus farmers do not harvest portions of hay fields or other potential forage areas infested with poison hemlock.
People may be poisoned by ingesting any part of poison hemlock. Poisoning cases have often occurred when an individual 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 (gloves, goggles, masks) when handling this plant.
Poison hemlock is an exotic plant species native to Europe and Asia. It was introduced into our country as an ornamental plant, which has escaped and has become an invasive plant moving its distribution across northwestern Ohio.
Clusters of tiny white flowers are borne on structures called umbels (look like upside-down umbrellas) on the upper part of the flowering stalks. Flowering season will last from now through August.
Poison hemlock (Conium maculatum) tends to have a biennial life cycle (lives for two years). It grows as a basal rosette the first year and 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; poison hemlock and wild carrot 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 hairs. Wild carrot plants are generally much shorter and the initial flowering period is later than poison hemlock.
Leaves look similar between poison hemlock and wild carrot. However, at all growth stages, leaves of poison hemlock tend to be bluish-green, strongly pinnately compound (fern-like), and the leaflet tips are sharp-pointed. Wild carrot leaves tend to be green, less pinnately compound, and have more rounded tips.
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 by 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 city 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 poison 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 on poison hemlock may found at the following addresses: http://bygl.osu.edu/node/757 and http://www.btny.purdue.edu/weedscience/2003/articles/PHemlock03.pdf.
On the farm front, corn planting and replanting was finished over the past weekend. Some farmers still have some soybean acres to plant or replant. Wheat is now in the grain-fill stages.

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