Flower:

Flat compound clusters (umbels) up to 6 inches across of 1/8-inch white flowers. Individual flowers have 5 petals, notched at the tip, 5 long stamens and a greenish white center. Flowers usually arise from a stalk in groups of 12-15, with 10 or more groups (umbellets) in a cluster. One plant usually has several clusters.

Leaves and stem:

Double compound leaves may be well over a foot long in the lower part of the plant and much smaller at the top; each compound leaf has 3 or more leaflets. Leaflets are up to 4 inches long and 1¼ inches across with pointed tips and sharp teeth. Leaflets often fold up some from the central vein. A distinguishing feature of the leaves is the veins radiating from the central vein tend to terminate in the notch of the teeth instead of the tip. The stem may be green or purple, or have purple streaks or spots.

Notes:

This is one of the most deadly poisonous plants in the U.S. to both humans and animals, and potentially invasive. The DNR recommends that if you find this on your property you should remove it immediately. It is easy to distinguish from other members of the Carrot family by the leaves.