The differences between Hemlock (Conium maculatum) and Cow's Parsley (Anthriscus sylvestris; also known as Wild Chervil)
As you see they are very similar in flower but the leaves are different. Leaf of Cows parsley is like that of a fern. Leaf of Hemlock is flat.If you are unsure do not give your horses anything from the hedgerows.
IF IN DOUBT DO NOT USE EITHER . ALWAYS CHECK YOU HAVE THE CORRECT HERB
Hemlock - Notice the flat leaves
Cows parsley- notice the fern like leaves