Perennials

Aconitum columbianum

Columbian Monkshood

Ranunculaceae

Western North America (British Columbia to New Mexico and Arizona)

At a Glance

TypePerennial
HabitUpright
FoliageDeciduous
Height2–6 feet (60–180 cm)
Width18–30 inches (45–75 cm)
Maturity3 years

Growing Zones

USDA Hardiness Zones

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

Key Features

Attracts Pollinators
Attracts Hummingbirds
Deer Resistant
Native to North America
Maintenancelow

Overview

Aconitum columbianum is an upright herbaceous perennial reaching 2–6 feet (60–180 cm) tall with a spread of 18–30 inches (45–75 cm) — height varying considerably by site moisture, elevation, and light. Stems are erect, branched in the upper portion, forming an open clump. Leaves are palmately divided, 3–6 inches (7.5–15 cm) wide, with five to seven deeply lobed and sharply serrated segments, medium to dark green. Flowers are blue to blue-violet, occasionally white or cream, with the characteristic arched hood (galea) of the genus Aconitum, produced on racemes from June through August, with bloom time varying by elevation and latitude. It is the primary native Aconitum species of western North America, found from British Columbia south to New Mexico and Arizona in moist mountain habitats. As with all *Aconitum*, all parts contain aconitine alkaloids and are highly toxic to humans, pets, and livestock.

Native Range

Aconitum columbianum is native to western North America, ranging from British Columbia and Alberta south through the Rocky Mountains and Cascades to New Mexico and Arizona. It occurs in moist mountain meadows, stream margins, seeps, and open woodland edges at elevations from 4,000 to 11,000 feet (1,200–3,350 m), typically in areas with consistent soil moisture from snowmelt or groundwater.

Suggested Uses

Planted in naturalized gardens, native plant borders, and moist woodland or meadow edges at 18–24 inch (45–60 cm) spacing, particularly in western North American landscapes. The blue-to-blue-violet flowers July–August and the native range make it suitable for habitat and pollinator gardens in the Pacific Northwest and Rocky Mountain regions. Suited to zones 3–7 in consistently moist, cool sites. Not suited to dry soils, hot-summer climates, or gardens accessible to unsupervised children or grazing animals.

How to Identify

Aconitum columbianum is identified in its native range by the hooded blue to blue-violet flowers on branched racemes, combined with deeply palmately divided leaves, 3–6 inches (7.5–15 cm) wide, with five to seven sharply serrated lobes. The hooded flower form of Aconitum is shared only with larkspurs (Delphinium), which have an open spur rather than a closed hood. A. columbianum is the only native *Aconitum* in most of its western range and is distinguished from introduced European species by native habitat association and slightly more branched inflorescence. Flower color varies from deep blue-violet to pale blue or cream.

Appearance

Size & Dimensions

Height2' - 6'
Width/Spread1'6" - 2'6"

Reaches mature size in approximately 3 years

Colors

Flower Colors

blue
violet
white

Foliage Colors

green
dark green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~8 weeks
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Summer
Blue to blue-violet hooded flowers are produced on branched racemes from June through August, with bloom time varying by elevation — plants at lower elevations bloom in June–July while high-elevation populations bloom July–August. Individual flowers are 0.75–1.25 inches (2–3 cm) long. Racemes open progressively from base to tip.

Detailed Descriptions

Flower Description

blue to blue-violet, occasionally white or cream

Foliage Description

medium to dark green

Growing Conditions

Sun Requirements

Full Sun
Partial Shade
Requires 3-8 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 consistently moist, humus-rich soil with a pH of 5.5–7.0 in partial shade to full sun. Water consistently — A. columbianum requires steady soil moisture and does not tolerate drying out; water weekly during dry periods. Performs best in cool, moist climates that approximate its native subalpine habitat. Tolerates full sun in cool-summer climates; afternoon shade is required where summer temperatures exceed 75°F (24°C). Performs in zones 3–7. Does not require division for many years if site conditions are adequate. All parts are highly toxic — wear gloves when handling.

Pruning

Cut stems to the ground in late fall after frost. Remove spent racemes after bloom if desired. Division is infrequent — established plants may persist without division for 5–8 years in adequate conditions. Wear gloves — all parts contain aconitine alkaloids.

Pruning Schedule

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fall

Maintenance Level

low

⚠️ Toxicity Warning

Toxic to pets and humans