Be careful around poison hemlock

I am glad to be back from medical leave. I have missed writing about agriculture and what is happening on the farm. Right now, the warmer than normal temperatures have induced poison hemlock to be in full flower — several weeks earlier than normal. It continues to be a problem weed in the area for city dwellers and farmers. Poison hemlock stands out as a tall plant with white flowers — plants may be six to eight feet tall. For those who are not familiar with it, it can easily be seen on the south side of the Trenton Avenue railroad overpass. It can also be found along roadsides, edges of fields, stream banks, fence rows and non-mowed areas. 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 should 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 confused poison hemlock roots for wild parsnip, leaves for parsley, and seed for anise. Though poisoning cases are rare, children have died from playing with whistles made from the hollow stems of poison hemlock. Illness has also occurred by 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. Wild carrot will have lacy bracts under the flower head, poison hemlock has no bracts. 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. Since poison hemlock is already flowering and maturing to the end of its life cycle, it is too late to control with herbicides. However, since it spreads by seed, removing the plants before seeds form and mature may prevent future plants. Once seeds mature, they may move to new areas by wind, birds, and rodents. If mechanically or physically removed, 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. Always wear protective clothing (long sleeves, long pants, socks, and shoes), gloves, goggles, and a dust mask while handling and working in poison hemlock areas. If poison hemlock plants have already gone to seed, note its current location. New plants will be back in these areas because of the seed along with plants still in the vegetative stage this fall. They can be identified by the fern-like rosette of leaves. At this stage they can easily controlled by herbicides. Spring herbicide applications will still 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, so it will kill grass and non-hemlock plants that the chemical contacts. 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: https://bygl.osu.edu/index.php/node/1218 and https://agcrops.osu.edu/newsletter/corn-newsletter/19-2021/putting-poison-hemlock-perspective.