In an earlier post we mistakenly stated that Proserpinaca palustris is categorized “S1” by the State of Vermont. This would mean that it is “Very rare (Critically imperiled): At very high risk of extinction or extirpation due to extreme rarity (often 5 or fewer populations or occurrences), very steep declines, or other factors.”
In fact P. palustris is listed as “S2”, a slightly less extreme category, meaning “Rare (Imperiled): At high risk of extinction or extirpation due to very restricted range, very few populations (often 20 or fewer), steep declines, or other factors.”
The source for this information is the Natural Heritage Information Project of the Vermont Department of Fish and Wildlife. You can find it on the 13th page of their document Rare and Uncommon Native Vascular Plants of Vermont. An explanation of the status codes and their legal implication s can be found here.