Aconitum carmichaelii 'Arendsii'
Common Name: azure monkshood 
Type: Herbaceous perennial
Family: Ranunculaceae
Zone: 3 to 7
Height: 2.00 to 4.00 feet
Spread: 1.00 to 1.50 feet
Bloom Time: September to October
Bloom Description: Azure blue
Sun: Full sun to part shade
Water: Medium
Maintenance: Medium
Flower: Showy
Tolerate: Deer

Culture

Best grown in moist, organically rich, well-drained soils in full sun to part shade. Soils must not be allowed to dry out, but need sufficient drainage to prevent wet conditions from developing. Best in full sun in cool summer climates. Appreciates some afternoon shade in the St. Louis area. Needs cool nights below 70 degrees F. to grow well, and, like the related delphiniums, will often struggle in hot St. Louis summers. Cut back stems after flowering to encourage an additional late season bloom. Although plants may be propagated by division, they are often slow to establish and are probably best left undisturbed once planted.

Arendsii Group plants may be grown from seed.

Noteworthy Characteristics

Aconitum carmichaelii is native to central China and is sometimes commonly called autumn-flowering monkshood because of its late summer to early fall bloom. It blooms later than most other species of Aconitum. It is an erect, tuberous-rooted perennial that features dense panicles (to 8” long) of hooded flowers atop rigid, leafy stems typically growing 2-3’ tall. In optimum growing conditions, plants may grow 4-5’ tall. Species flowers are deep purple inside and paler blue outside. The upper sepal of each flower develops into a large, helmet-like structure that somewhat resembles the hood worn by medieval monks, hence the common names of monkshood and helmet flower. Leathery, dark green leaves are deeply divided into 3-5 lobes. All parts of the plant (especially the roots and seeds) are extremely poisonous. Arendsii group hybrids (A. carmichaelii x A. carmichaelii var. wilsonii) feature uniformly deep azure blue flowers. Species is sometimes sold as A. fischeri.

Genus name is the Latin name from the Greek akoniton used for these poisonous herbs.

Specific epithet honors medical doctor and plant collector Dr. J.R. Carmichael (d. 1877).

The upper sepal of each flower develops into a large, helmet-like structure that somewhat resembles the hood worn by medieval monks, hence the common names of monkshood and helmet flower.

'Arendsii' is the result of a cross between A. carmichaelii and A. carmichaelii var. wilsonii. Plants have some variability and are often referred to as Arendsii Group. This monkshood flowers in fall (later than most other species of monkshood) and is accordingly sometimes commonly called autumn-flowering monkshood. It is an erect, tuberous-rooted perennial that features dense panicles (to 8” long) of hooded, deep azure blue flowers atop thick, rigid, leafy stems typically growing 2-4’ tall. 'Arendsii' stems are unusually thick (more so than most other monkshoods) and are less likely to need support. The upper sepal of each flower develops into a large, helmet-like structure that somewhat resembles the hood worn by medieval monks, hence the common names of monkshood and helmet flower. Leathery, dark green leaves are deeply divided into 3-5 lobes. All parts of the plant (especially the roots and seeds) are extremely poisonous. 'Arendsii' honors German nurseryman Georg Arends (1863-1952) who first bred this cultivar about 1945 at his nursery at Ronsdorf-Wuppertal near Cologne.

Problems

No serious insect or disease problems. Crown rot, powdery mildew and verticillium wilt are occasional problems. Generally does not need staking or other support. WEAR GLOVES WHEN WORKING WITH THIS PLANT. Avoid skin or oral contact with plant juices, and be particularly careful to cover up any open cuts or skin abrasions prior to entering garden areas.

Garden Uses

In the St. Louis area, this plant needs consistently moist soils and may be best grown in moist woodland areas, along streams or ponds, or on the periphery of bog or water gardens. Will grow in borders as long as the soil moisture requirements can be met. Because of the poisonous properties of the plant, it probably should not be grown in areas where small children might come in contact with it or in areas contiguous to vegetable gardens where tubers are growing.