All I am going to say this week with regards to planting progress in Clinton County is … Rain, &%*#$# rain, go away!

Please pray for the farmers that still have acres to plant this year. Oh yeah, while you are at it, tell a farmer “Thank you” for all they do to help get food on our tables. It is years like this they need our support. It has been stressful to say the least this planting season.

For the rest of my article this week, I want to focus on a weed that is seen throughout the county called poison hemlock. Hemlock is in the Apiaceae or parsley plant family, which also includes wild carrot (Queen Anne’s lace), wild parsnip, cow parsnip, and giant hogweed.

Poison hemlock has been in Ohio for a long time, and there are many areas it is never subject to any control measures such as abandoned fields and woodland borders. Other areas one can find and see poison hemlock include edges of fields, ditch banks, roadways, hay and pasture fields etc.

These are areas that it could or should be controlled, especially where it may pose a risk to quality or safety. Poison hemlock is poisonous to animals and humans, but it is important to understand poisoning occurs only when ingested.

To an animal, it has a strong odor and tastes bad, so unless there is nothing else out there to eat, animals tend to leave it alone.

However, it can end up inadvertently in hay bales – where it does retain toxicity. For hemlock, toxins will remain viable and lethal regardless of the curing process and storage methods of hay. All parts of the plant are poisonous, with the seed heads being the most toxic.

For us humans, I would not eat any plant I do not know what it truly is. Some accidental poisonings in the U.S. have occurred due to people mistaking poison hemlock for Queen Anne’s Lace (Wild Carrot) in which the flowers of it can be eaten.

Poison hemlock contains eight piperidine alkaloids, with coniine (mature plants) and g-coniceine (young plants) being the two predominant toxic compounds. Experimental hemlock poisoning in livestock has shown a wide range of clinical signs suggesting variation in the toxic alkaloid content in the plant.

Cattle eating as little as 300 grams up to 0.5 percent of body weight has shown to be fatal. Bluish discoloration of the skin from poor circulation, respiratory paralysis, and coma without convulsions are common signs before death, which usually occurs within 2-3 hours after consuming a lethal dose.

Contact with hemlock can also cause skin and eye problems which are way more likely than internal poisoning.

The severity of this response varies depending upon the sensitivity of the individual and the degree of contact. This happens only with direct contact with plant parts or fluids from the plants.

Anyone mowing or removing hemlock by hand should keep this in mind and protect themselves from skin and eye contact.

I have also read suggestions to not mow large populations of poison hemlock in an open tractor because tiny plant parts or juices can become airborne and could be ingested resulting in possible poisoning.

Poison hemlock is a biennial weed. It spends the first year as a basal rosette and the second year as an erect, towering flowering plant that can measure 6-10 feet tall.

Leaves are alternate, pinnately compound, finely divided, toothed, and glossy green. Stems are branched, waxy with purple blotches, hollow between nodes, and grooved.

It flowers usually in June through August, but this year it has been flowering for a few weeks already. The flowers come in clusters of small white flowers with 5petals in a loose umbrella-like cluster 2-7 inches across. It has a fleshy taproot.

Poison hemlock is on the Ohio noxious weed list. Therefore, it needs to be controlled before becoming large enough to present a threat and before seed production occurs to prevent spread. Information on the Ohio noxious weed law can be found here: .

Applying herbicides

At this time of the year when these plants are flowering, producing seed, and dying, it’s not always possible to use chemicals to control them. The goal should be getting rid of existing plants through cutting, mowing, or hand removal, and limiting production and spread of seed.

The most effective timing for the application of herbicides is fall when plants are low-growing rosettes in their first year of growth, or early the following spring when plants are still small.

Suggested herbicides and their respective effectiveness ratings can be found in Table 21 of the “Weed Control Guide for Ohio, Indiana, and Illinois”, which lists pasture and CRP herbicides.

There are additional products labeled for roadsides, industrial areas, etc. but they will not be included in this guide.

There is an excellent article online at that has excellent pictures and does a nice job of presenting information on the other species within the Apiaceae or parsley plant family, including identification of wild carrot (Queen Anne’s lace), wild parsnip, cow parsnip, and giant hogweed.

As always, for more information or questions, please feel free to contact me at [email protected] or contact out office at (937) 382-0901.

Tony Nye is the state coordinator for the Ohio State University Extension Small Farm Program and has been an OSU Extension Educator for agriculture and natural resources for over 30 years, currently serving Clinton County and the Miami Valley EERA.

Tony Nye

OSU Extension