Perennials

Aconitum napellus

Common Monkshood

Ranunculaceae

Central and western Europe (Pyrenees to Carpathians and Balkans)

At a Glance

TypePerennial
HabitUpright
FoliageDeciduous
Height3–5 feet (90–150 cm)
Width18–24 inches (45–60 cm)
Maturity2 years

Growing Zones

USDA Hardiness Zones

3 - 8
Zone 3
Zone 4
Zone 5
Zone 6
Zone 7
Zone 8
These zones indicate the coldest temperatures this plant can typically survive.
Frost Tolerancehardy

Key Features

Attracts Pollinators
Deer Resistant
Maintenancemoderate

Overview

Aconitum napellus is an upright herbaceous perennial reaching 3–5 feet (90–150 cm) tall with a spread of 18–24 inches (45–60 cm), forming a dense erect clump. It is the type species of the genus and the most widely cultivated monkshood, parent to many of the common garden cultivars including the bicolor and hybrid selections. Leaves are palmately divided, 3–6 inches (7.5–15 cm) wide, with five to seven very deeply and narrowly cut lobes, dark glossy green — more finely dissected than most other commonly grown *Aconitum* species. Flowers are deep violet-blue with the characteristic arched hood (galea), produced on dense erect unbranched racemes 12–18 inches (30–45 cm) long from June through August. Stems are erect and may require staking at the taller end of the height range in exposed sites. Aconitum napellus contains aconitine in concentrations among the highest of any temperate garden plant — all parts are highly toxic to humans, pets, and livestock, and skin contact with sap can cause alkaloid absorption and numbness.

Native Range

Aconitum napellus is native to mountain meadows, stream margins, and moist open woodland edges in central and western Europe, from the Pyrenees east to the Carpathians and Balkans, at elevations of 3,000–8,000 feet (900–2,400 m). It has been cultivated in European gardens since at least the medieval period and is naturalized in parts of North America.

Suggested Uses

Planted in partially shaded to lightly sunny borders and woodland garden edges at 18–24 inch (45–60 cm) spacing. The dense deep violet-blue racemes June–August are the defining feature of the classic shade border midsummer display. Suited to zones 3–8 in consistently moist, cool sites. Not suited to dry soils, hot-summer climates without consistent afternoon shade, or any garden setting accessible to unsupervised children or grazing animals due to the very high toxicity of all plant parts.

How to Identify

Aconitum napellus is identified by the very finely and deeply dissected dark glossy green leaves — more narrow-lobed than most other cultivated *Aconitum* — combined with dense, unbranched erect racemes of deep violet-blue hooded flowers from June through August. The deeply cut leaf lobes with very narrow segments are the most reliable vegetative identification feature distinguishing it from the broader-lobed hybrids and cultivars derived from it. The erect, unbranched (as opposed to branched) raceme structure further separates it from A. carmichaelii.

Appearance

Size & Dimensions

Height3' - 5'
Width/Spread1'6" - 2'

Reaches mature size in approximately 2 years

Colors

Flower Colors

violet
blue

Foliage Colors

dark green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~8 weeks
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Summer
Deep violet-blue hooded flowers are produced on dense unbranched erect racemes 12–18 inches (30–45 cm) long from June through August, lasting 6–8 weeks. Individual flowers are 1–1.5 inches (2.5–4 cm) long. Racemes open progressively from base to tip.

Detailed Descriptions

Flower Description

deep violet-blue

Foliage Description

dark glossy green

Growing Conditions

Sun Requirements

Partial Shade
Full Shade
Requires 2-6 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.0(Neutral)
357912
Soil Types
loamclay
Drainage
moist

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

2–3 years

Care & Maintenance

Care Guide

Plant in moist, well-drained, humus-rich soil with a pH of 5.5–7.0 in partial shade to full sun where summers are cool. Afternoon shade is required where summer temperatures regularly exceed 75°F (24°C). Water consistently — water weekly during dry periods; does not tolerate drying out. Mulch to retain soil moisture and keep the root zone cool. Performs in zones 3–8. Divide clumps every 3–4 years in early spring to maintain vigor. All parts contain high concentrations of aconitine alkaloids — wear gloves at all times when handling and keep away from children and pets.

Pruning

Cut stems to the ground in late fall after frost. Deadhead spent racemes promptly; a second flush of smaller racemes sometimes follows in late summer. Divide in early spring before significant foliage emergence. Wear gloves — all parts contain high-concentration aconitine alkaloids; sap contact with broken skin should be avoided.

Pruning Schedule

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fallearly spring

Maintenance Level

moderate

⚠️ Toxicity Warning

Toxic to pets and humans