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Aconitum spp.

monkshoods

Ranunculaceae

Temperate Northern Hemisphere: Europe, Asia, North America

Attracts Pollinators Deer Resistant

Native to North America

SunFull Sun – Part Shade

WaterMedium

HardinessZones 3–8

Overview

Aconitum spp. is a genus of about 250 species of herbaceous perennials in the family Ranunculaceae, native to the mountains and moist woodlands of the Northern Hemisphere. Most species form upright clumps 2 to 6 feet (60 to 180 cm) tall from tuberous or fibrous roots, with deeply palmately lobed, dark green leaves. The flowers are carried in terminal and branched racemes, each bloom with an arching upper sepal that forms a hood or helmet over the smaller inner parts, the source of the names monkshood and helmet flower. Across the genus, flower color spans deep blue, violet, purple, white, pink, and yellow, with bloom mainly in mid- to late summer and autumn. All parts of every species contain aconitine and related diterpenoid alkaloids, which are highly toxic, and ingestion or absorption through broken skin can be fatal. The genus grows in cool, moist, humus-rich soils in part shade to full sun and declines in heat and drought. A limitation is its low tolerance of dry, hot conditions, under which foliage scorches and plants weaken.

Native Range

Aconitum spp. is native to the Northern Hemisphere, across temperate Europe, Asia, and North America. The genus is concentrated in mountain meadows, stream banks, and moist woodlands, with its greatest diversity in the mountains of central and eastern Asia.

Suggested Uses

Aconitum spp. species are used in the middle and back of moist borders, in woodland and streamside plantings, and in cottage-style schemes where their late bloom extends color into autumn. The blue-flowered species are grown with asters, anemones, and grasses in cool-climate gardens.

How to Identify

Identify Aconitum spp. by its hooded flowers, in which the uppermost of five petal-like sepals arches over the rest to form a helmet 0.5 to 1.5 inches (1.3 to 3.8 cm) tall. The leaves are dark green and deeply cut into 3 to 7 toothed lobes in a palmate arrangement. Upright, often branched flower spikes rise above the foliage in summer and fall. The tuberous roots separate many species from the fibrous-rooted Delphinium spp., which has spurred rather than hooded flowers.

Appearance

Size & Dimensions

Height2' - 6'

Width/Spread1' - 2'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Summer Fall

Aconitum spp. flowers from mid-summer into autumn, roughly July through October depending on species and climate. Bloom opens from the base of each raceme upward, and branched stems extend the display over several weeks. Some early species flower in late spring.

Detailed Descriptions

Flower Description

blue, violet, purple, white, and yellow

Foliage Description

dark green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 3-6 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

loam clay

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

2-3 years

Care & Maintenance

Care Guide

Across the genus, Aconitum spp. grows in cool, moist, humus-rich soil in part shade, tolerating full sun where summers stay cool and soil stays moist, with a pH of about 5.5 to 7.0. Plants are slow to establish and are left undisturbed once sited, as the brittle tuberous roots are easily damaged by division. Tall species may need support in exposed positions. Consistent moisture is needed through the growing season, and plants weaken in hot, dry sites. All parts contain aconitine alkaloids that are absorbed through the skin, so contact with cut roots and foliage causes numbness and irritation in sensitive individuals. Mulch conserves soil moisture and keeps roots cool.

Pruning

Spent flower stalks can be cut back after bloom to tidy the clump, and some species produce a smaller second flush of bloom when deadheaded. Foliage is cut to the ground after it dies down in late autumn. Cut stems and roots release sap containing toxic alkaloids.