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Aconitum bicolor
bicolor monkshood
Europe, western Asia (hybrid origin)
Overview
Aconitum bicolor is an upright herbaceous perennial reaching 3–5 feet (90–150 cm) tall with a spread of 18–24 inches (45–60 cm), forming an erect clump of deeply divided foliage topped by racemes of hooded flowers in late summer. Leaves are palmately divided, 3–6 inches (7.5–15 cm) wide, with five to seven deeply cut lobes and sharply serrated margins, dark green and glossy on the upper surface. Flowers are bicolor — white with blue-violet to purple margins and a hood (galea) — arranged in elongated racemes 12–18 inches (30–45 cm) long from July through September. The hooded galea enclosing the upper petals is a genus-level trait of Aconitum spp.. Stems are erect and self-supporting in sheltered sites but may fall at 4–5 feet (120–150 cm) when unstaked in exposed or heavily fertilized conditions. Aconitum bicolor is treated as a hybrid or intermediate form between A. napellus and A. variegatum. All parts of the plant contain aconitine alkaloids in concentrations lethal to humans, pets, and livestock in very small doses; skin contact with cut stems can cause numbness in sensitive individuals.
Native Range
Aconitum bicolor is of garden or hybrid origin, combining traits of A. napellus and A. variegatum. Both parent species are native to mountain meadows, stream margins, and alpine woodland edges of central and western Europe at elevations of 2,000–8,000 feet (600–2,400 m).Suggested Uses
Planted in partially shaded borders, woodland garden edges, and stream-side plantings at 18–24 inch (45–60 cm) spacing. The bicolor white-and-blue-violet late-summer flowers on tall erect stems extend the bloom sequence in shade borders past midsummer. Suited to zones 3–7 in cool, consistently moist sites. Not suited to hot-summer climates above zone 7, dry soils, or gardens frequented by unsupervised children, pets, or livestock due to high toxicity of all plant parts.How to Identify
Appearance
Size & Dimensions
Height3' - 5'
Width/Spread1'6" - 2'
Reaches mature size in approximately 3 years
Colors
Bloom Information
Bicolor white-and-blue-violet hooded flowers appear on elongated racemes 12–18 inches (30–45 cm) long from July through September, with a total bloom period of 6–8 weeks. Individual flowers are 1–1.5 inches (2.5–4 cm) long. Racemes open progressively from base to tip over 3–4 weeks.
Detailed Descriptions
Flower Description
white with blue-violet to purple margins and hoodFoliage Description
dark glossy greenGrowing Conditions
Sun Requirements
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
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 reduces heat stress where summer temperatures exceed 75°F (24°C). The species does not tolerate dry soil; water weekly during dry periods throughout the growing season and mulch to retain soil moisture. Performs in zones 3–7; heat tolerance declines sharply above zone 7. Established clumps are divided every 3–4 years in spring to maintain vigor. All parts contain aconitine alkaloids and are lethal on ingestion to humans, pets, and livestock in small doses.Pruning
Spent flower racemes can be cut back to the basal foliage after bloom, producing a secondary flush of smaller racemes in some seasons. Stems are cut to the ground in late fall (October–November) after frost. Division is carried out in early spring (March), before significant foliage emergence. Cut stems release sap containing aconitine alkaloids that can be absorbed through skin abrasions.Pruning Schedule
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fallearly spring