How to get rid of poison hemlock for good

(Photo: Jan Samanek, State Phytosanitary Administration,’ll find poison hemlock along fencelines and ditches around this time in Ohio, and it’s a weed livestock owners cannot afford to ignore because all parts of this plant, including leaves, stems and roots, are poisonous when ingested.

I thought poison hemlock awareness was increasing significantly, but then reality hit me.

While driving back from Cincinnati to Marietta, with my family, we stop to explore the Serpent Mound in Peebles, Ohio. While making our way there, we saw a farm selling hay, so I stopped to ask how much since I was running low this year due to the lack of forage production at the beginning of the growing season.

As I was pulling up to the house, I couldn’t help but notice all the 1-foot poison hemlock plants, so I jokingly asked the farmer if he was in the business of growing poison hemlock or milking cows.

He quickly replied, “Well, I guess both.”

After pointing it out and describing the effects to him, he mentioned that his cows were “acting funny” the other day and thought they got into something. He had no idea this invasive plant was on his farm and quite frankly, never gave it much thought.

It can kill

Poison hemlock is highly toxic to humans and livestock when ingested — either in its vegetative growth stage and when dried.

Typically, grazing animals will avoid poison hemlock because of its unpalatable taste unless there is little other feed or forages available or when it’s consumed through hay.

When consumed, poisoning symptoms appear rather quickly which includes: bloody feces, vomiting, paralysis, trembling, loss of coordination, pupil dilation, coma and eventually death from respiratory failure.

How to control

Poison hemlock can be controlled quite easily. I completely eradicated it from my farm in two years using nothing but a machete, a little patience and botany.

In the summer of 2015, the county township asked if they could spread soil along my property to help build-up and stabilize the road since the road was 4-5 feet higher than my pasture.

At the time, I said yes, but I did not realize the soil source came from road ditches that the county had been clearing.

When spring of 2016 rolled around, the amount of junk weeds that appeared along my property was heartbreaking, and, of course, poison hemlock was among the junk weeds.

Since poison hemlock is a biennial (a plant that takes two years to grow from seed to fruition and die — this is where botany comes in to play), I used a little patience and waited for the plant to flower.

One week after the plants flowered, I simply chopped them down at the base and discarded the plants over the hill and away from livestock. By cutting the plant down after flowering, I eliminated its potential to produce more seeds.

At this time, the plants did not have enough reserves to shoot up another flowering stalk.

In the spring of 2017, I had a few more plants bolt up (leftover 2015 seeds that germinated in 2016), so I simply repeated what I did the year before to control it.

Now in 2018, I did not have a single plant bolt up and all it took was patience, botany and a machete.

Of course, if this plant has been present on your property for a while, it may take you up to 3-5 years to completely eradicate and exhaust the soil’s seed bank. Poison hemlock seeds are viable for only 3-5 years.

What does it look like

The first step to controlling poison hemlock is being able to recognize the plant. Right now is a great time to identify the plant, because currently, poison hemlock is somewhere between 2 to 5 feet — with the potential to reach heights of 10 to 12 feet in moist conditions.

Leaves are dark glossy green, fern-like, triangular, and 3-4 times pinnately compound (as shown in the picture). Probably the most distinguishing feature is the plant’s smooth hairless purple-spotted stem, which is hollow between the nodes.

Once the plants start to flower, they will be small, white, and found in umbrella-shaped clusters.

Looks like wild carrot

Sometimes poison hemlock gets confused with wild carrot (a.k.a.: lace flower, Queen Anne’s lace). However, wild carrot has hairs along its slender stem and leaf bases while poison hemlock’s stem is smooth and purple-spotted.

Peak bloom for poison hemlock is in late May and early June, whereas wild carrot is just beginning to produce flowers. Wild carrot will only reach heights of 3 feet or less.

Also, poison hemlock is more branch-like than wild carrot.

Take action

Once poison hemlock is successfully recognized and confirmed, the next step is to take action to control it.

Besides using my method of mechanically controlling the plant (hand-pulling, whacking, cutting, mowing, etc.) chemical control is also a viable option. Since poison hemlock is a biennial, it is best to control first-year plants by applying herbicides in the fall, and for second-year plants, applying herbicides in the spring before the plant gets too large.

According to the Ohio State University Weed Control Guide, Crossbow and Remedy Ultra has the best rating for controlling poison hemlock (rating of 9) followed by glyphosate (Roundup), dicamba, and Cimarron Max, which all have a rating of 8.

It is important to note that these herbicides are either broadleaf killers (including legumes) or nonselective (kills both grasses and legumes). For light infestations, spot treatment may be the preferred method.

Remember, poison hemlock is one of Ohio’s 21 noxious weeds and should be controlled.

For more information on poison hemlock or help with identifying it, contact your local Extension office.


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Marcus McCartney is an OSU Extension agriculture and natural resources educator in Washington County. Send questions or comments to or write c/o Farm and Dairy, P.O. Box 38, Salem OH 44460.


  1. Why wait to flower? We have an acre and this hemlock was introduced with a load of soil. we have been having a hard time getting rid of it. We try not to use chemicals, but wow. For homeowner keeping on top of this has been tough.

  2. Hi Linda, Typically when doing mechanical control, like chopping a plant down, if you chop it early, before it flowers, it still has plenty of energy in the root to send up a shoot (albeit usually shorter) and then flower and go to seed. If you chop it after it has flowered, often, as Marcus wrote in his article, it won’t have the energy to recover at that point in its life-cycle, and you won’t see it sprouting back up and setting seed.

  3. What about mowing them down vs machete? I would mow to the middle and gather and dispose of, as well as clean mover so as not to spread to the rest of the property.
    Thank you,

  4. Yes – you can mow them down but keep in mind, if you mow them down now, you’ll have to make multiple mowings because the plant should have enough energy in its taproot to shoot up another reproductive stalk. Keep monitoring the site for regrowth and cut/mow as needed. Th goal with mowing is not let the plant develop flowers.


  5. Just be careful not to get the sap/juices on your skin and definitely do not ingest it. Covering your skin and wearing gloves is recommended.

  6. We’ve been digging up the plants and getting most of the root on the big ones. So since it is a bi-annual, does that mean any small pieces of the root that break off will not regrow?

    • I shouldn’t regrow but this depends on the time of year you are digging it up and the stage of plant growth.

  7. I have noticed poison hemlock spreading everywhere on my 40 acres. I have used Roundup and it comes back. I’ve pulled it out in one meadow…but it’s back. I bought a flame thrower. Can’t use it on poison ivy because the flame vaporizes the poison and humans can then breath in the poison. Would torching the hemlock be the same risk? I also can cut and gather the cuttings with my leaf picker upper on the flat portions of my property but it is in the ravine and woods where I can’t take the mower. …and then, what does one do with the piles of cuttings? I hate using Roundup and other chemicals…

    Thank you for any help

    • Laurie and Brian,

      The plants keeps coming back due to new plant seeds germinating. For an area to be completely eradicated of Poison Hemlock, the soil’s seedbank needs to be exhausted. A weakness of poison hemlock is a short viable seed life; around 5 years – relatively short compared to other plants which can be up to 30 years or longer. Seeds which germinated this season, will be forming rosettes close to the ground. These rosettes can be sprayed with an effective herbicide; killing the plant and creating no bolting situation the following season. Or, wait until next season to cut it down when the plant has bolted and flowered to control it. Again, it will take up to 5 years or so to completed eradicate the soil seedbank; especially if it has been allowed to buildup.

  8. Laurie, it’s coming back because seeds are still in the soil. In theory you should be able to eradicate a biennial by taking care of it for two successive years. But there are always exceptions with seeds that take longer to grow. Keep at it and you will be successful. My late brother in law had loads of soil delivered and spread over a new septic bed. When I moved to help my sister after he died, I found a forest of 8-10 foot tall blooming plants.

  9. What about tilling? We had a forest of hemlock that we pulled out when they were large. Now sprouts are coming out. They are small enough that they can be easily disturbed with tilling. Could tilling alone act as eradication at this early stage?

  10. Do NOT burn it!! The smoke from it is poisonous and sent my neighbor to the hospital. I’ve also read on the Oregon Extension Service site that the dead stalks can remain toxic for 3 years

  11. Question – Does its poison transfer to other plants it has touched or does one have to actually eat the hemlock itself to be poisoned. Can I eat plants it is growing through as long as it has been completely removed or not? It is growing through my young carpet of gardened greens and wild greens (such as chickweed in the yard) for the first time and I’m pulling it all out by hand while it’s still tiny. But I want to know if I’m going to have to wait until next year to eat anything where it has been (assuming there’s none of it again next year).

  12. This is a great discussion. Here in California it is an issue, spreading from side of road and creek areas to farms and meadows.
    I have been battling my landlord who wants to keep mowing and tilling them in versus my approach to no spray and hand weeding after flower for a few years. I am literally looking at 1000s that came up this year, from only a few very large established from last year.
    My theory is that the tiller (without asking before hand spread them around on my (edible) farm field) spread the seeds around extensively and now I have to watch and prioritize for the next few month. :/
    Im going to invest in a new sharp machete!!
    I am going to let the cut stalks sit in a corner for a few years.
    I too wonder if the ones mowed and tilled in or small ones growing with other plants will effect the safety of consumables growing next to them.

    Thanks All!

  13. I’ve discussed this with a hay farmer as this is an every growing issue in the Midwest. They use 2-4-D to knock it out. I know depending on the season will determine the application steps and how many rounds of it needed. Has anyone had experience with 2-4-D?

    • 2,4D is a contact killer, and not systemic – meaning the chemical will not translocate (move) throughout the plant. Therefore, timing is very critical when spraying 2,4D. According to the 2020 OSU Weed Control Guide, 2,4D had a rating of 7 – meaning it is 70%-80% effective in controlling poison hemlock. In comparison, Glyphosate (Round-Up) has a rating of 8 (80%-90% control) and Crossbow has a rating of 9 (90% – 100%).

  14. I am battling this on railroad property where a few have ended up on my property. I cut them down after flowering and then sprayed weed killer this month. There are much more this year than last. Would cutting them all down help?

    • If last year was your first year battling this plant by cutting it down after flowering, ending seed production, then you can expect to fight this plant for another 3-5 years until the seed bank is exhausted; especially along the railroads – they seem to be polluted with this noxious weed.

      What you are seeing now, if the first year growth. You can kill these plants with chemicals now or wait until next year (the plant’s second and final year) to cut it down after flowering (the plant only flowers in second year). If you cut down or mow the first year, the plant probably has enough energy in its reserves to shoot up more growth. Spraying is probably your most effective method at this stage.

  15. Are there precautions that should be taken when cutting poison hemlock with a machete? Should I be concerned with the plant contacting my skin or sap that may end up on my boots and pants?

    I know poison ivy and and the yellow flowing cow parsnip causes blisters after exposure to the plant oils/sap. Does exposure to poison hemlock cause a similar reaction?

    This years batch of poison hemlock is everywhere and I would like to cut as much as I can.


    • Hi Cathie,

      Yes, I would avoid getting the sap on your skin. It does cause blister. I got a little on my wrist recently, and I had a small red rash, but it doesn’t itch like poison ivy. So, long sleeves, long pants, shoes and socks, and gloves is recommended when cutting it down. As for the boots, simply make under control swipes with your manchette, cutting near the base of the plant. Making low under control cuts will prevent foliage and other plants material from flying everywhere, by keeping the plant in one large piece.

    • Only if the seeds were viable, and if not, then it wouldn’t matter. If viable seeds did get thrown away, then temperature, moisture, air, and light conditions must be correct for germination to occur. Poison Hemlock’s seed life is short, 3-5 years, meaning the clock is ticking for these seeds to meet the conditions above to germinate.

  16. Not much was said about the purple stem of the plant. Is it not a standout measure of recognition of the hemlock plant?

    Thanks for the excellent information on the plant. The Toussaint River is in my back yard so I will be checking out the area looking for these poisonous plants now that you have sounded the alarm.

    • Absolutely. The purple spotted/streaked stem is an excellent identifiable characteristic to use when accurately identifying Poison Hemlock.

  17. I see several questions about the effect of Hemlock on other edible plants in a garden but no responses. I just pulled out a 2’ plant by hand which hadn’t flowered yet, before finding this great article! It was in my garden and about 12-14 inches from my squash plant. Do I need to worry about this and other nearby tomato plants?

  18. I understand waiting until it flowers to cut it down, BUT, ABSOLUTELY do not come in contact with skin or breath any of the pollen or spores from the plant. Just breathing anything that comes off the plant can kill you. Wear complete protective clothing, mask, gloves, goggles. It’s nothing to mess around with! I have seen large patches of it everywhere, and I don’t think people are aware this innocent looking weed is so dangerous!

    • Actaully, there is no reseach stating the pollen is toxic. There is no literature saying if it is or is not poisonous.
      More than likely it is not but we need more resreach. I have been around the plant numerous times when flowering and never suffered any symptoms from breathing in pollen, not has any of my colleagues.
      Messgae from OSU insect chemical ecologist specialist:
      The secondary compounds of poison hemlock, Conium maculatum, are primarily alkaloids. I am not familiar with studies looking at the levels of these compounds in floral nectar and I could not find anything after a quick review of the literature, so I have to answer your question in more general terms. Plant secondary compounds have primarily evolved to reduce herbivory. It is not surprising then that levels of secondary compounds, such as the alkaloids of Conium, tend to be absent or at lower levels in plant nectars since pollinators are beneficial to the plant. In fact, at the levels found in nectar, some alkaloids often are actually therapeutic to pollinators, e.g., by reducing gut pathogens (Irwin et al. 2014). Another ecological role demonstrated for nectar alkaloids is to reduce the duration of each flower visitation by pollinators. This causes the pollinator to visit more flowers, increasing the number of flowers pollinated and reducing the plant costs of pollination (Wright et al. 2013).

      Irwin RE, Cook D, Richardson LL, Manson JS, Gardner DR. 2014. Secondary compounds in floral rewards of toxic rangeland plants: impacts on pollinators. J Agric Food Chem. 62:7335–44.
      Wright GA, et al. 2013. Caffeine in floral nectar enhances a pollinator’s memory of reward. Science.339:1202–4.

      Although there are some examples of “toxic nectars,” the fact that I did not find any references for poison hemlock suggests it is not one of them. Also I did see it on a list of nectar sources for a tiny parasitoid wasp, which also suggests it is not toxic to insects.

  19. I read about this last year. I came across it this year in its second season of growth; it is flowering. I cut it down to the ground and put it in the back of my truck as it is too long to put into a plastic bag. Is it okay to cut up and do that? I wore gloves. I wore long pants, socks, and only exposed areas were face, neck, and arms. I gather I need to wear goggles, a mask, and long sleeves. I was over-whelmed when I saw it all over the place in what used to be dad’s cattle feedlot. I gather I need to cut it and spray it or spray it, let it sit and cut it. My husband didn’t believe me at first but having read about it last year, I had a feeling that this was the dreaded poison hemlock. It says it can become a perennial if the conditions are favorable. What do you think about that? If the life span is 3 to 5 years, it could just keep producing plants that would come back forever so I guess if you put 3 to 5 years into it and it is gone….that is great. I just hope at 68 I have that time.

    • Hi. Cutting it up to fit in a bag is fine. The plant’s life span is not 3-5 yrs. The seed in the soil is only good (viable) for 3-5 yrss. The plant is a biennial. After it flowers – it’s finshed.

  20. I have several of the poisonous Hemlock plants on my property and by the road, I am cautious mowing around these plants but do indeed definitely want to get rid of it. From what I have been reading with your cutting suggestions I will see what I can do to get a full body throw away suit and head gear. I have a very bad reaction to nettles and concerned about the reaction to poisonous Hemlock.
    After I manage to get it all cut down should I be aware that it might take up to 5 years to completely get rid of it?

  21. I use long extended handled shears to cut instead of a machete, less effort.

    Good info on the seeds,(3-5 years) and time to cut off flowers.

    My question is : if you cut off just below the flower and leave the stem will that keep the flower from seeding and keep the shoot from producing another flower?

    • Hi John, Great question. Yes – the plant will not produce any more flowers since it’s at the end of its life cycle and doesn’t have the resrves to produce more reproductive flowers.

  22. If you can find Good Housekeeping, April 2022, there is a good article on the danger of hemlock and the medical problems this man had after unknowingly cutting hemlock with a chainsaw. He almost died. They determined he had breathed in little particles in the air from using a chainsaw!

  23. I recently read an article about a gentleman that ended up in the hospital for almost a year. He had to be put on a ventilator. He had been clearing his property and had unknowingly cut poison hemlock with a chain saw. The breathing in of the particles from the Poison Hemlock from cutting it down had caused blood clots though out his body. The article said the best way to get rid of it is to pull it out if you are able or to spray it with herbicide. Never cut it.

  24. I found about four or five plants in a low area last year on my property in northern MN. My wife determined it was hemlock and I decided to snip off the flowers before they went to seed in July. I disposed of them in a black garbage bag. This year I have found about a dozen plants. Several are right next to our driveway where we walk so I tried vinegar and salt. It killed one young plant but only delayed growth in others. Some are just starting to develop flowers so I want to cut them soon before they go to seed. I will probably just cut them near the bottom so they cannot develop flowers and of course wear protective gear and a mask. What do I wash the lopers with afterwards to make sure I get the sap off. Would a sharp shovel work to slice through at ground level versus lopers or would that risk disturbing more seeds?

    • You can simply wash off the plant juices with soapy water. A bleach solution is not necessary since the goal is to remove the plant’s juices from the metal, not sterilize it from pathogens, however you can wipe down with an alcohol wipe after washing as a two-step process to make sure all the juices are removed. A sharp shovel sounds like a great idea. You can use anything which will cut the plant cleanly and easily.

  25. I’m planning on digging the whole root up! I plan too cut the plant into small pieces too fit into a large trash bag. Wish me luck! I plan too use a pruning scissors! I have a full face respirator is the full face respirator necessary? I’ll use nitrile plastic exam gloves and maybe wear a cloth coverall with a zip up running up the front from the crotch too the neck.

    • A full respiratory is not necessary. Only you know how sensitive you are to various plants. If you do not feel comfortable handling the plant without a full respirator, then please wear one for your own peace of mind.

  26. This was so helpful, I plan on following these instructions but, I think I also want to terroform this land as well. I belive I am going to cut & clear, then cover for a month with woven ground cloth, then put pigs in the same area with a mobile style fencings & then plant pumpkin where the pigs were, harvest the pumpkins, put the pigs back in there to eat left over pumpkins etc, move them and then plant throw and grow. I may het volunteer pumpkins all the time from. That area but I’d rather have pumpkins then helmlock.

  27. For a large area with a long established patch would it make sense to clear the area then use permanent heavy duty weed barrier for a few years instead of cutting, uprooting or spraying? We bought a 10 acre neglected foreclosure property and the thought of maintaining 2+ acres thick with poison hemlock for the next 5 years seems overwhelming. Has anyone else tried this method? Couldn’t find much on this approach elsewhere. Advice and thoughts on this approach would be appreciated.

  28. A Never ending Battle here along a Creek. lots of wildlife tracking it in. It has become my life goal to eradicate it from my fields. Thanks for the article. I have sprayed 3 acres out of 30. will try cutting as they flower but with this much to cut It may get the upper Hand.

  29. This showed up in my yard. Only 2 were flowering, the rest were all in the rosette stage but I must have pulled / dug up at least two dozen rosettes of various sizes this afternoon, most of them were very small. Wore all the protective gear but goggles (I wear glasses anyway). The problem now is that its all over the front yard as well. The backyard was the priority because we have dogs and they like to graze the grass at times and I’m TERRIFIED that they’ll nab grass that has hemlock sprouts in it. Even now, I’m so anxious that it’s still in the grass and just not grown enough for me to have spotted it. Because of the pets, weed killers aren’t an option but I don’t think anything natural (like vinegar) is strong enough to kill this stuff.

    My biggest concern is, is it safe to mow when it’s still in the rosette stage? I don’t want to let my lawn become an overgrown mess because I’m too scared of disturbing this death carrot. We also pay to have our lawn mowed and I don’t feel comfortable putting someone’s health and potentially their life at risk if I ended up missing some and they mow it down. I’m also really concerned about that in the backyard as well, not just it being in the air but then tiny pieces of it being spread EVERYWHERE in the yard and the dogs eating grass that has tiny bits of hemlock on it.

    It’s stressing me out to the point that I want to strip the yards bare, completely till it, and lay new sod. Would that even help or would it just grow through the sod as well if theres more seeds?

  30. I’ve found water hemlock all along a small stream that runs through my yard. Would this approach work for water hemlock as well? I started trying to dig out small plants by the roots, but I’m unable to tease the roots out from other plants, and I don’t want to handle it too much, so I’ve been throwing away shovelfuls of soil to do the job. I would like to eradicate it completely, even if it take five years, but is this an exercise in futility if the neighbor upstream doesn’t do any management?

    • Waterhemp is a summer annual, so the control method will differ than those of the biennial poison hemlock. My first question is, are you able to hand pull the plant? Or cut, and do follow up clippings?

      Since Waterhemp is a prolific seed producer and able to produce as many as 1.5 times more seeds than about 250,000 seeds per plant, it is important to prevent seed production. Like poison hemlock, its seed-life is fairly short and only remain viable in the soil for several years. Research has shown that only 1 to 12 percent of waterhemp seeds remain viable in the soil seedbank after four years.

      However, being near a streambank, new seeds can easily wash on shore annually. To keep it at bay, periodic scouting and observations are key to make sure it is eradicated and doesn’t establish a foothold again.

      • Thank you for your reply. Is water hemp the same as spotted water hemlock?
        I’m willing to dig, but I’m losing so much muddy soil to the process because it’s impossible to tease the roots out from the growth around it in the muck. There is an accompanying overgrowth of reed canary grass, dock, and others.
        I’m willing to cut, of course, and appreciate the need to prevent seeds from being distributed.
        I’m desperate to get rid of it to protect our dog, who indiscriminately grabs plants in her teeth as she wanders. She’s lost her off-leash privileges since we found the plants.
        I’d like to educate myself about the general management of the vernal pond and ephemeral waterway, so if you have any sources or social media accounts to share, I’d appreciate that.

  31. Hi. Thank you for the valuable info. I found some pretty large plants today. In regards to flowering- Do i need to wait for all the clusters to actually bloom open or is it ok to cut when only the very top clusters are starting to bloom?

    • It may be ok to cut now, and if you do decide to cut it down now, I recommend observing the site a few days after cutting to see if any regrowth is occurring.
      If you decide to wait until the plant’s flower process is complete, then there should not be any regrowth. I typically wait to make my cuts one or two weeks after flowering.

  32. Once you cut the Poison Hemlock what is the best way of disposing it? I dont want to dump it on my property somewhere and it sounds like burning it is a bad idea too.

  33. I ended up just cutting them all down 4 inches from the ground and then making a pile of them and covered it with black plastic sheeting. Figure the sun could do the work of killing it for me.

  34. Hi there. I noticed some come up on my property last year and cut the plants after flower. I also was able to locate the source of the seeds (golf course edges across the street) and they were kind enough to remove the thousands of plants when I explained what they were and how it could endanger their clients looking for stray balls. I had a rather thick patch that I brush hogged and then put heavy black plastic over. I’m wondering if you know what temperature will kill the seeds? It is in full sun and according to the thermometer gets up to 150 on a 75° day. Thank you. The article was extremely helpful. If you have any suggestions on killing off the 5 acre patch of phragmites I’m all ears.

  35. I have a small field that was overgrown with briars, so I had someone bushhog it for me last fall. This spring when I mowed it for the first time I noticed the water hemlock. It seems like every time I mow there’s more of it!
    If I just keep mowing so it doesn’t go to seed, will it eventually be eradicated?

  36. Hello Marcus,

    This is the best information I’ve found on this subject. Thank you for continuing to monitor the posts.

    I have somewhat of a technical question that I can’t find the answer to anywhere: when cutting down the flowering plant as described above, when in the flowering process is it too late to simply cut it down and let it lay, versus needing to bag the flower / seed head? I’m not a biologist and I don’t know how long it takes for a flower to become a viable seed.

    Thank you again!


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