Poison Hemlock
Conium maculatum · Herbaceous Biennial (Not a true tree, but often reaches shrub-like heights)
Plant Family
Apiaceae (Carrot Family)
Tree Category
Invasive Weed / Poisonous Herb
Variety / Cultivar
None (Wild species)
Hardiness Zones
USDA Zones 3 through 10; extremely adaptable to varied climates.
About This Tree
A tall, erect herbaceous plant that can look like a small tree or shrub. Distinguishable by its hollow, hairless stems with purple spots/blotches and fern-like foliage. The plant is highly toxic if ingested and can cause skin irritation.
Leaf Characteristics
Brilliant green, lacy, fern-like leaves. They are 3-4 times pinnately compound, triangular in overall outline, and emit a rank, mousy odor when crushed.
Bark Characteristics
Not a tree, but the 'trunk' (main stem) is light green, hollow, hairless, and marked with distinctive purple or reddish spots or streaks.
Growing Information
Origin Region
Native to Europe, Northern Africa, and Western Asia; widely naturalized and invasive in North America.
Growing Season
First year forms a basal rosette; second year produces tall flowering stalks in late spring to mid-summer, then dies.
Sunlight & Water Needs
Full sun to partial shade; prefers moist soils but is highly adaptable to dry areas, roadsides, and waste grounds.
Mature Size
Typical height of 5 to 8 feet (can reach 10 feet), with a spread of 2 to 4 feet; rapid growth rate in its second year.
Special Characteristics
Extreme toxicity to humans and livestock; contains coniine. Highly invasive; often confused with wild carrot (Queen Anne's Lace) which has hairy stems without purple spots.
Wildlife & Ecology
Generally avoided by most wildlife due to toxicity; some specialist insects may use it, but it typically displaces native vegetation and reduces biodiversity.