This herbaceous perennial flower fills a number of garden needs, and it’s one of the few almost true blue flowers. Although it is native to mountainous areas, it is quite heat-tolerant. Monkshood is a tall plant that blooms late in the summer and handles partial shade very well. It gets its common name of monkshood from its resemblance to the cowl on monk’s habits. There are about 250 species of aconite, but Aconitum napellus is the most commonly grown ornamental variety.
All parts of Aconitum are poisonous if ingested or if the sap comes into contact with any mucous membrane. Effects range from skin irritation to cardiac and respiratory failure. Always wash your hands after handling monkshood. You’ll find many references in literature to monkshood being used to kill enemies. Another common name for monkshood, wolf’s bane, refers to its use for getting rid of wolves. Do not grow this plant around young children or curious pets.
That said, monkshood has been safely cultivated in gardens for hundreds of years. It is a lovely flower, just use caution when handling it.
- Leaves: Smooth palmate leaves with deep lobes.
- Flowers: Racemes of blue or white flowers are borne on sturdy, unbranched stems. There are 5 sepals and the top sepal curves downward, giving the flower its hood-like appearance. The actual petals are hidden inside the hood.
Wolfsbane, Wolf’s Bane, Helmet Flower
Monkshood is reliably perennial in USDA Hardiness Zones 4 through 8. In ideal conditions, it has been known to survive down to Zone 2.
The plants can handle both full sun and partial shade, however, they prefer somewhat moist soil. If you are growing them in a hot, dry area, definitely give them a spot with some shade, especially in the afternoon. When grown in shade, you will probably need to stake the plants.
Monkshood fills out to a nice size plant, reaching a height of 3 to 5 ft. and spreading to 1 1/2 ft. However, it does take several years to become established. Once established, the plants are very long-lived.
Flowering starts in mid- to late summer and will continue into the fall.
- Soil: Monkshood plants prefer a soil pH that is neutral to slightly acidic, but will tolerate other soils as long as they are rich, moist, and well draining.
- Starting from seed: You can start monkshood from seed, but it can be finicky about germination and may take a year or more to sprout. Start extra seeds and don’t expect them all to germinate. Sow the seed from fall to early spring. They need to go through a chilling period, to break dormancy. The plants don’t really like to be transplanted, so direct sow if possible. They can be ephemeral their first year, so don’t panic if they disappear.
- Planting: Monkshood likes a fairly rich soil. Add plenty of organic matter before planting to add nutrients and to help keep the soil moist, but draining well. You can plant or divide monkshood in either spring or fall, but avoid doing it in the heat of summer. Monkshood never “needs” dividing, but you can divide it if you want more plants. The roots tend to break easily, so handle with care. They are easier to divide if you water them beforehand so that the soil adheres to the roots.
- Water: Once established, monkshood is able to withstand short periods of drought, but for robust plants, provide a moist soil or water regularly.
- Fertilizer: Feeding always depends on the quality of your soil. Definitely start with rich soil, high in organic matter. Side dress with compost and some organic fertilizer each spring.
- Maintenance: Monkshood are very low maintenance plants. Since these are late season bloomers and they do not repeat bloom, you won’t really need to deadhead. The plants will die back to the ground at frost.
- Design tips: Pair monkshood with other moist, shade lovers like astilbe, Hosta, heucuera, and hellebores. Since they are tall plants, they are usually relegated to the back of the border.
Pests and Problems
Problems with monkshood are rare, especially if they have good growing conditions. They are deer resistant. In fact, because of its poisonous qualities, most animals avoid the plant.
- Insects: Fourlined plant bug and leafminers can mare the leaves. Mites can also stress the plants.
- Diseases: Susceptible to bacterial leaf spot, rust, and verticillium wilt.
Some people are extremely partial to the common unnamed monkshood because of its intense, rich color and easy growing habit. However, there are a handful of worthy cultivars and species, if you can find them:
- Aconitum septentrionale "ivorine": Very early blooming with elongated, white flowers.
- "Albus ": The familiar monkshood with, as the name implies, white flowers.
- "Blue sceptre": If you can’t decide on blue or white, this variety has bicolor flowers.
- Aconitum hendyi "spark's variety": This one has branched flower stalks, giving it a fuller appearance.