Monkshood (Aconitum): Deadly Beauty for the Shade Garden

One of the first perennials grown as an ornamental, monkshood (Aconitum) remains popular centuries later. Beyond classic blue, cultivars now offer white, pale blue, pink, and yellow. But beware: this is among the most toxic garden plants.

Plant Profile

~250 species, mostly tall (1–2 m), long-lived perennials from moist Northern Hemisphere mountains. Smooth, deep green, glossy, deeply lobed palmate leaves. Terminal racemes of hooded flowers (modified sepals) mid-summer to fall. The upper sepal forms the signature "helmet." True petals are reduced to nectaries inside the hood.

Culture

Back-of-border plants. Full sun or part shade; sun-grown plants are wind-resistant, shade-grown may need staking. Evenly moist, well-drained soil; pH adaptable. Thick taproot resents transplanting—sulks first year, then rebounds vigorously. Transplant in fall.

The Deadly Side

All parts, especially roots, contain aconitine alkaloid. Stimulates then paralyzes pain, touch, and temperature nerves on mucous membranes. Abraded skin absorbs dangerous doses; tasting can be fatal. Native peoples poisoned arrow tips for millennia. "Wolfsbane" may reference werewolf mythology—repelling or causing lycanthropy.

Caution: Wear gloves. Avoid if small children are present. Educate older kids. Accidental poisonings occur.

Not Alone in Toxicity

Datura, castor bean, foxglove are also highly poisonous yet popular. Monkshood's virtues—long-lived, easy, showy, tough—balance the risk with knowledge.

Key Species and Cultivars

• A. napellus (common monkshood) – Widest Eurasian range. Deep blue; 'Album' (white). Hybrid × cammarum yields 'Bicolor' (blue/white), 'Eleonor' (white/blue margin), 'Carneum' (grey-pink), 'Roseum' (pink), 'Bressingham Spire' (violet-blue), 'Newry Blue' (near black-blue), 'Stainless Steel' (pale blue), 'Pink Sensation' (true pink).
• A. henryi – To 2+ m, sprawling, branched stems; needs support. 'Spark's Variety' stiffer. Zone 4. Central/western China.
• A. carmichaelii – Latest bloomer (into October), extends fall season. 'Arendsii' (85–120 cm, dense dark violet-blue racemes) great cut flower. Zone 3. Central/western China.
• A. columbianum – Native North American, to 2 m, scattered violet-blue flowers. Good for informal areas. Var. bakeri (45–60 cm) for rock gardens. Zone 3.
• A. lycoctonum (wolfsbane) – Pale yellow, narrower flowers, mid-summer. Popular in Europe. 'Ivorine' (cream, 80–100 cm). Zone 3.
• A. anthora – Compact (45–75 cm), yellow, standard hood shape. European. Zone 5. Mid-border use.
• Dwarf/alpine species (Himalayas, Yunnan) – 30–60 cm, 3–10 large flowers. Blue-violet standard. A. biflorum, A. bhutanicum. Gems: A. hookeri, A. naviculare (10 cm!). Zone 5–6.
• Twining species – 1–2 m, vine-like. Scattered flowers on upper stems. A. delavayi, A. hemsleyanum, A. vilmorinianum, A. volubile, A. tanguticum, 'Red Wine' (dark wine).

Photo credits: kennedyh, bonniewong, veshengo. (Editor's Note: Originally published March 18, 2008.)