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Michigan's Invasive Species Community

Thoughts on poison hemlock?

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Over the past 2 years we have had a few occurences of poison hemlock, just 1-4 plants each, within our CISMA. This is very new to the area. I have heard that it is prevalent on roadsides south of Michigan, being opportunistic of disturbance. 

I noticed on Michigan Flora that there are known occurrences both north & south of the six counties of NCCISMA.

Has anyone seen this species actively outcompeting natives and impacting habitat (beyond the ROWs)?

Since the risk to human health comes from eating it, which is a bad idea for a lot of plants, I do not think the risk to human health qualifies it as invasive.

Wondering if I should make control of poison hemlock a priority?

Insight and input on this would be appreciated!

Edited by Vicki Sawicki
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  • 2 weeks later...

We've been managing one area of poison hemlock at Quincy Mine dry house ruins for several years. We pull the PH out by it's taproot and bag it. We are now down to several hundred small stems that fit in one large contractor bag. If left, it was heading to be a monoculture-like infestation. I visited an area west of Denver in the foothills this summer and saw crazy infestations of PH, which a friend of mine eliminated from his yard by annual pulling, so yes I have seen them outcompeting natives but on drier, upland sites. And annual manual control works well.



Edited by Sigrid Resh
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We have a small infestation in Marquette city limits, though for being small it got incredibly dense incredibly quick - like within a year after discovering. Ours was in a riparian area at a road dead-end. We were able to do a chemical treatment last year, as our first year we were miserably unprepared with PPE for manual removal. While ingestion is the most common way for poisoning, we were lucky enough to time our manual efforts with its full-blown-pollen stage, which can apparently be anywhere from irritating to deadly depending on how much you inhale. So it does pose a significant risk, and if you have a small patch and can get on it quickly, I'd definitely recommend prioritizing it so it stays small!

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