Many monkshoods look similar to delphiniums (to which they're related). Like delphiniums, monkshoods have spikes of flowers in shades of blue, purple, white, and yellow. Up close, the individual florets resemble hooded faces. In addition to the attractive flowers, the plants have dark green, divided foliage. Some species, such as A. hemsleyanum, grow as perennial vines and need the support of a trellis. Monkshoods are good cut flowers-if you can bear to take the beauties out of the garden.
- Common name: Monkshood, wolfsbane
- Botanical name: Aconitum spp.
- Zones: 3 to 8, depending on species
- Size: To 10 feet tall, depending on species
- From: Areas of Europe and Asia
- Family: Ranunculaceae (ranunculus family)
- Sun: Partial shade
- Soil: Moist, but well-drained soil rich in organic matter.
- Moisture: Keep the soil moist, but not wet.
- Mulch: A 2- to 3-inch-deep layer of mulch around the plants is beneficial, especially in warm-summer or dry areas. This layer of mulch helps conserve soil moisture and prevents the soil temperature from becoming too warm.
- Pruning: Cut down dead stalks in autumn after they freeze or in early spring before the plants begin to grow.
- Fertilizer: In soils rich in organic matter, extra fertilizer isn't usually necessary. In other soils, use a general-purpose fertilizer in spring.
- Staking: To stake the tall plants, sink a tall stick or stake into the ground a short distance from the plant (so you don't harm the root system), and tie the plant stem to the support. It is best to use a figure-eight pattern to tie the plant with the stem in one loop and the stake in the other. This helps prevent excessive rubbing, which can cause disease problems.
- Seed: Sow seed in autumn-as soon as it is ripe-either in a cold frame or sheltered spot in the garden in a moist, seed-starting mix. The seeds should germinate in the spring, though it can take more than a year after sowing. It generally takes several years for the plants to flower from seed.
- Division: Divide large clumps in spring or autumn. It may take the plants some time to recover from division as they resent disturbance. Transplanting monkshoods can also prevent them from flowering for a year or two.
- Aphids: Aphids generally attack in large numbers. The insects are very small and variously colored. Try repeatedly spraying them from plants with a stream of water from the garden hose; encourage beneficial insects; or apply insecticidal soap or horticultural oil.
- Fungal diseases: Deter them by pruning the plants to encourage good air flow, avoiding wetting the foliage, and mulching the soil around the plants.
- Gray mold: Gray mold starts out as a leaf spot and may develop into fuzzy, gray areas on the plant.
- Leaf spot: In summer or autumn, the leaves become spotted yellowish or with darker colored spots. Each spot often has concentric rings around it, forming something of a bull's-eye pattern.
- Powdery mildew: In mid- to late summer, affected leaves have a grayish powdery covering. The leaves then drop off.
- Rust: Usually looks like leaf spotting that's followed by small masses of rust- colored powder on the leaves. Infected leaves die by the end of the season.
- All parts of the monkshood plant are poisonous-especially the roots.
- Gardeners with sensitive skin may notice skin irritation if they come in contact with the plant's sap.
- Aconitum x cammarum ‘Bicolor': Grows about 4 feet tall and bears spikes of white and blue flowers in mid- to late summer. Zones 3 to 7.
- Aconitum x cammarum ‘Bresshingham Spire': Grows about 3 feet tall and bears spikes of blue flowers in mid- to late summer. Zones 3 to 7.
- Aconitum carmichaelii: Grows about 6 feet tall and bears spikes of blue or purple flowers in early autumn. Zones 3 to 7.
- Aconitum carmichaelii ‘Arendsii': Grows to 4 feet tall and bears spikes of blue and white flowers in early autumn. Zones 3 to 7.
- Aconitum hemsleyanum: Vine climbing to 10 feet with clusters of purple flowers midsummer to autumn. Zones 5 to 8.
- Acontium ‘Ivorine': Grows to 3 feet tall and bears spikes of creamy white flowers in early summer. Zones 5 to 8.
- Acontium lyctotonum: Grows about 5 feet tall and has creamy yellow flowers in summer.
- Acontium napellus: Grows to 5 feet tall and bears spikes of blue or white flowers in summer. Zones 5 to 8.
- Acontium napellus ‘Carneum': Grows about 5 feet tall and has spikes of pinkish flowers in summer. Zones 5 to 8.
- Acontium ‘Spark's Variety': Grows to 5 feet tall. Bears spikes of blue-purple flowers in summer. Zones 3 to 7.