Not that I've ever heard of. The toxins in _Conium_ are alkaloids, which I
don't think it secrets and which I don't believe plants could take up intact.
My biggest worry would be making sure there were no seedlings of hemlock
coming up. One could mistake them for carrots and .....
>I planted a garden in an area that was previously covered by poison
>hemlock. Does poison hemlock release toxins into the soil that could be
>taken up by the vegetables now growing in the garden?