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Can someone tell me what this is? I've got a TON of this on a new property I just moved to.

Located in Dayton, Ohio, USA

What is this?

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    For identification questions, the location in the world of your new property is useful for improving accuracy. Don't need enough accuracy to send you a letter, but Ireland, Manitoba, Panama and Tasmania all have rather different flora, for example.
    – Ecnerwal
    May 12, 2015 at 3:22
  • Reminds me as being a relative of Hemlock, be careful with it till you identify it as members of this family can be very poisonous. May 12, 2015 at 4:14
  • I'd also say some Apioideae. Not blooming yet, I think? But pictures would come in handy if available... Size judging by the dandelion stalk and the leaves on the right probably three feet / scant 1m? And I assume you are in Europe?
    – Stephie
    May 12, 2015 at 6:08
  • Ohio, US, actually, and 3-4 feet. May 12, 2015 at 6:33
  • Well Hemlock grows in the US, too. Do you see any ridges on the stalk or is it smooth? Is the surface "dusty" like ripe plums are sometimes? Hollow stalk? If you do cut, be careful, there's a good chance that it is hemlock, the red splotches would say so.
    – Stephie
    May 12, 2015 at 6:39

3 Answers 3

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Definitely in the Apiaceae Family. I considered Anthriscus sylvestris (called cow parsley or Queen Anne's Lace) at first, but looking at it a bit more, I'm pretty sure it's Conium maculatum (Hemlock). Fortunately I found a website discussing the differences between the two. From what I can see in your pictures the stems appear rounded rather than grooved, suggesting Hemlock. Also the red dots on the stem are suggestive of Hemlock.

I would suggest clearing it out CAREFULLY before it flowers. Wear gloves and a long sleeved shirt so the sap doesn't get on your skin, if it does wash it off fast. The sap has the potential to cause localized burning/rash on your skin, but it's only lethal if you eat it.

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    CERTAINLY NOT Anthriscus sylvestris - I have seen my fair share of these. Neither size nor stem are right. Ifthis were in Europe, Aethusa cynapium might be a candidate which is quite similar to hemlock, but that's typically not found in the US. Both poisonous, though.
    – Stephie
    May 12, 2015 at 10:44
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The University of Missouri identifies it as poison hemlock (Conium maculatum L.). Look here - - http://ipm.missouri.edu/IPCM/2012/2/Weed-of-the-Month-Poison-Hemlock/

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    Can you expand on this as link only answers do not provide enough context if the link changes. Why do you think it is hemlock?
    – kevinskio
    May 10, 2016 at 0:45
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I agree that this is Conium maculatum, poison hemlock. The big tip-off for identifying it is the purple spotted stems, which if you look closely also have a glaucous (whitish-waxy) coating, and are not hairy. Contrast with other similar-looking species like carrot / queen anne's lace (Daucus carota) which has hairy stems and usually lacks the purple spots. Also notice the multiply-compound leaves that are fine-textured and kinda fernlike. Although I do not recommend touching it with bare hands, it also has a distinctive and unpleasant smell.

In North America it is an invasive plant, and it is also highly toxic. I would recommend removing it but urge caution.

Removal is doable but safety precautions are important; although it does not usually cause contact dermatitis in small amounts, the toxin can be absorbed through the skin and I think there is at least one case of a fatality involving exposure through trying to weed it. I have worked with it extensively and I always limit my work to a dry day, cover up fully, long sleeves and gloves, and limit the amount of time I spent with the plant to a half hour at a time, to be safe. It is probably also best to wear a mask, according to the Purdue University Extension.

Except in the hardest, most compacted soils, it is generally easy to uproot, using a large shovel for the largest ones or just a hand trowel for most plants. It usually grows in moist, rather deep soils where it is easy to remove.

It is a biennial, and I find its long-term persistence in the seed bank is low, so if you remove all flowering plants, there will be less of it the second year, perhaps a few plants the third, and it is often gone after that point except for isolated plants which might be re-colonizations from distant populations. I have had good luck permanently removing it from a site and having it not come back at all after about 3 years.

The easiest time I've found to remove it is right before it flowers, as you can grab hold of the stem. However, the plant is more toxic around this time; it may be safer to remove earlier in the season if you can catch it when it's smaller, and especially it is best if you can spot the first-year plants that just have a basal rosette, and pull them out with a trowel.

If you want to replace it with a plant in the same family but that are safer to have around, and locally-native, you can look at Thaspium trifoliatum, and perhaps Zizia aurea. Both of these are native to your area, I think Thaspium trifoliatum might do a little better. I think they would probably grow pretty well in similar conditions, Thaspium on the drier side of those conditions and Zizia on the wetter side.

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