A member of the Apiaceae (Carrot) family Poison-hemlock is a biennial native to the Europe and North Africa and is a common weed, widespread in California. Poison-hemlock may germinate throughout the year. First year plants are low-growing and may overwinter in mild climates and plants resemble carrot plants. Stems are erect, hollow, smooth and bright green with purple-reddish blotches. Leaves grow to two feet long and are tri-pinnately compound. In late spring, robust plants reach 5-8 feet tall and produce numerous umbel-shaped clusters of tiny, white, 5-petaled flowers. Poison-hemlock grows in moist areas such as pond sides, creek
banks and flood plains. It tends to grow in dense thickets and when the plants have dried out it is very difficult to walk through and the dead canes are toxic! It is notorious for displacing other vegetation. Plants reproduce only by seed and seeds may survive to about 3 years. Each flower produces two gray–brown seeds. There are hundreds of seeds on each plant. Poison hemlock is highly toxic due the toxin coniine. Seeds have the highest concentration of coniine. All parts of the plant are poisonous. Cattle are especially vulnerable. There are limitations to controlling this plant: do not cut, burn or graze. Pulling it is one of the best options and it’s especially important to pull out the root.
-Mark Skinner, Invasive Species Chair