That is more likely Torilis arvensis. Conium maculatum has large basal rosettes and complex leaves like the ones shown below. It gets to 6 or 7 feet tall ... much larger than the Torilis candidate in your photos.

Don't mean to hijack the thread. Until I saw jekees pic of poison hemlock, I was calling this plant Conium m. Now I'm not so sure.

Old Forester, see if Osmorhiza longistyllis (Sweet Cicely) fits.

Yes, I think it is Torilis arvensis (hedge parsley/tall sock-destroyer), as its flower petals seem wider and larger away from the center than those of Conium maculatum (Poison Hemlock) - which seems to have uniformly narrower petals in even 5-star patterns.

Hedge Parsley is what's actually responsible for those notorious Velcro wedge sock burrs!

Conium maculatum flowers are in denser umbels and the stems are smooth, not ridged, often with purple blotches.

I'm still confused, Conium maculatum vs Cicuta maculata . I don't think my plant is Osmorhiza. Some more pics of the leaves. Plant is now 2' tall

Underside

Stem is 3/4" and smooth

That isn't Conium maculatum. Compare the leaves with those in jekeesl's photo above and in their post at this link..

I'm asking if its Cicuta maculata?

Cicuta maculata does look good. Thanks for the new photos.

Thanks, I didn't realize there were 2 poison hemlocks.

Old Forester, here is a nice listing of all the "hemlocks" -- http://www.wildflower.org/expert/show.php?id=12540

Great info, thanks. Now, do I leave or eradicate. A large tree blew over couple years ago and the void left, lets in enough light so that they are spreading !