Poisonous hemlock a problem weed

Poisonous hemlock continues to be a problem weed for city dwellers and farmers. It is often found along roadsides, edges of fields, stream banks, fence rows, and non-mowed areas. It is currently in full flowering stage and easy to see since plants can reach heights of six to eight feet tall. Poison hemlock plants contain highly toxic piperidine alkaloid compounds, including coniine and gamma-coniceine, which cause respiratory failure and death in mammals. All parts of the plant are considered poisonous, but the roots are the most toxic. 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 infested with poison hemlock. The toxins must be ingested or enter through the eyes or nasal passages to induce poisoning. This plant should not be handled because sap on the skin can be rubbed into the eyes or accidentally ingested while handling food. Gloves, goggles, and a mask should be worn when working around this weed. There have been cases were people were poisoned when they confused hemlock roots for wild parsnip, leaves for parsley, and seed for anise. 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 L.) tends to have a biennial life cycle (lives for two years). It grows as a basal rosette (like a dandelion plant) 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 L.), and wild parsnip (Pastinaca sativa L.), 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, water, 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 them 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, goggles, and a dust mask while handling. Mowing or cutting with a weed-trimmer before flowering can be effective. Wear a dust mask and goggles to avoid inhaling toxins and contact with eyes while mowing or cutting. At this time, note patches of poison hemlock. Plants will be back in these areas because of seed. Use mechanical or chemical control on these patches before plants bolt two years from now. Look for the fern-like rosette of leaves this fall or early next spring. They can easily be controlled by broadleaf herbicides at this time. 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/2499 and https://www.canr.msu.edu/news/poison-hemlock-identification-and-control.