Cicuta maculata aka Spotted Water Hemlock

Cicuta maculata is water hemlock, also called spotted cowbane. This North American herb belongs to the carrot family, Apiaceae. It grows in wet meadows, swamps, thickets, and floodplains. It also grows beside ponds, streams, and roadside ditches. The plant is native to North Carolina and the Midwest. It is not native to Britain or Ireland. Sources describe it as perennial, though NC State also lists biennial growth.

Young plants form a low rosette in their first year. A tall, upright stalk develops in the second year. It can reach 8 feet [2.44 metres] in height. The plant grows fast and has short, tuberous roots. Its smooth, hollow stems branch and bear purple stripes or blotches. Internal walls divide the stems at their nodes. Green leaves grow in an alternate pattern and clasp the stem. They divide into leaflets in two or three pinnate tiers. Lower leaves reach 1 foot [0.30 metres] long. Leaves near the top are smaller. Leaflet veins end in the notches between the teeth. This feature helps distinguish it from other carrot-family plants.

Tiny white flowers grow in compound umbels above the leaves. These clusters can reach 0.5 feet [0.15 metres] across. Each cluster holds smaller groups of flowers. The blooms may have a faint scent. Chicago Botanic Garden lists flowering from May through October. Nectar draws bees, wasps, flies, moths, and butterflies. Black swallowtail caterpillars use the plant as a host. Each fruit holds two seeds and stays closed when ripe. Water birds eat the fruits.

Water hemlock grows in full sun or partial shade. It suits moist soil and tolerates spells of wet ground. NC State lists sandy and loamy soils rich in organic matter. It accepts acid to neutral soil. Chicago lists USDA zones 3–5, while NC State lists 5–9. Sources list borders, naturalized areas, and butterfly gardens as uses. It reproduces from seed and can self-seed. Aphids can attack its flowers and leaves.

Its severe poison risk outweighs these garden uses. No part is safe to eat, and roots are most poisonous. Eating it can cause seizures, stomach pain, and death. ASPCA identifies cicutoxin as its toxic substance. It poisons dogs, cats, and horses as well as people. Signs can include tremors, fever, diarrhea, and breathing failure.