Monkshood care comes down to cool, moist, rich soil and careful handling. The Royal Horticultural Society says common monkshood (Aconitum napellus) grows best in deep, cool, moisture-retentive soil in partial shade, and that every part of the plant is toxic if eaten, so you should avoid skin contact and wear gloves. Grow it where summers are cool, keep the soil evenly moist, and keep it away from children, pets and vegetable beds.
| Need | What the sources say |
|---|---|
| Light | Partial shade; full sun only if the soil is humus-rich and mulched (RHS); afternoon shade in warmer areas (NC State; Illinois) |
| Soil | Deep, cool, moisture-retentive (RHS); humus-rich, moist, well-drained (NC State) |
| Hardiness | USDA zones 3 to 7 (NC State) or 3 to 8 (Illinois); grows better in cool-summer areas (NC State) |
| Size | 3 to 4 feet tall, 1 to 1.5 feet wide (NC State) |
| Bloom | Mid to late summer (RHS); September to October in Illinois |
| Planting | Tuberous roots in fall, crowns just below the soil surface (Illinois) |
| Toxicity | High; all parts poisonous; may be fatal to people and pets (NC State) |
Sources: RHS; NC State Extension Plant Toolbox: Aconitum; University of Illinois Extension: Common Monkshood.
What Is Monkshood?
Monkshood, also called aconite or wolfsbane, is Aconitum, a genus of over 250 species of herbaceous perennials in the buttercup family, Ranunculaceae (NC State Extension). The common garden species, Aconitum napellus, is an upright, clump-forming perennial with deeply divided dark green leaves and tall spires of violet-blue, hooded flowers (RHS). NC State also lists white and lavender-flowered forms in the genus.
Don’t confuse it with winter aconite
Winter aconite (Eranthis hyemalis) is a different, low-growing plant with yellow flowers in late winter. Monkshood’s leaves also look a lot like delphinium and larkspur, so label it clearly in the garden.
What Conditions Does Monkshood Need?
The RHS says monkshood grows best in deep, cool, moisture-retentive soil in partial shade, tolerating full sun only where the soil is humus-rich and mulched. NC State says it grows better in cool-summer areas and needs afternoon sun protection in the southern part of its range, and University of Illinois Extension recommends sun with afternoon shade.
Light
Morning sun and afternoon shade, or dappled shade. In cool northern gardens it can take more sun if the soil stays moist.
Soil
Rich in organic matter, evenly moist and well drained. Work compost into the bed before planting, and avoid dry, sandy spots.
Climate
Hardy to USDA zone 3. It struggles in hot, humid summers, which is why it’s far more common in northern and mountain gardens.
How to Grow Monkshood: Planting
- Choose the spot carefully. Illinois Extension says monkshood is difficult to divide and transplant successfully, so plant it where it can stay. Keep it away from vegetable beds: NC State warns its fleshy roots could be mistaken for Jerusalem artichokes.
- Plant in fall or spring. Illinois Extension recommends planting the tuberous roots in fall with the crowns just below the soil surface. Avoid burying the crowns deep.
- Space plants for airflow. NC State lists a spread of 1 to 1.5 feet; give them room so leaves dry quickly after rain.
- Wear gloves for all planting and handling, as the RHS and NC State advise.
- Mulch and water in. A layer of mulch keeps the soil cool and moist, which the RHS notes matters if the plant gets more sun.
Pro tip: Mark the planting spot. Monkshood dies back in winter, and its roots are easy to damage or dig up by accident in spring.
Watering and Feeding
Illinois Extension says moisture should be consistent but not overly wet and swampy. Water deeply during dry spells so the soil never dries out completely, especially in summer, and water at the base rather than over the leaves to help limit mildew. A top-dressing of compost in spring feeds the plant and helps hold moisture. For choosing a fertilizer, see our guide to synthetic vs organic fertilizer.
Pruning and When Monkshood Blooms
The RHS lists flowering in mid to late summer, and Illinois Extension reports blooms from September through October, so timing varies with climate and variety. NC State says to cut back after flowering to encourage more blooms; the RHS notes no pruning is needed beyond cutting back dead stems. Tall stems may need staking, according to NC State. Wear gloves for all pruning, and don’t compost or burn the cuttings where people or animals could be exposed; bag them for the trash.
Does Monkshood Spread?
Monkshood is a clump-forming perennial (RHS) with a slow growth rate (NC State), so it spreads gradually as the clump widens rather than running through a bed. It can also self-seed; removing faded flower spikes before they set seed limits that. If a clump gets too big, the RHS suggests dividing it in autumn or late winter, but warns that divided plants may be slow to re-establish, and Illinois Extension calls it difficult to divide and transplant.
Can You Grow Monkshood in Containers?
It can be grown in a large, deep container with rich, moisture-retentive mix and drainage holes, but pots dry out and heat up faster than garden soil, which monkshood dislikes. Keep the pot in partial shade, water often, and place it where children and pets can’t reach it. Monkshood is not a houseplant; it needs a cold winter rest outdoors.
Is Monkshood Poisonous?
Yes: highly toxic to people and pets
NC State Extension rates monkshood’s toxicity as high. All parts, including roots, leaves, flowers and seeds, contain aconitine and other alkaloids, and NC State says it is poisonous if ingested and may be fatal to humans and pets. Listed symptoms include burning of the lips and mouth, numbness of the throat, intense vomiting and diarrhea, muscle weakness and spasms, a weak pulse, respiratory paralysis and convulsions. The RHS says to avoid skin contact and wear gloves when handling it.
- Always wear gloves when planting, pruning or dividing, and wash your hands and tools afterward.
- Don’t plant it near vegetable gardens or where children play or pets dig.
- If someone eats any part, call Poison Control at 1-800-222-1222 (US) or emergency services right away. For pets, call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435.
For safer garden and houseplant choices, see our list of cat safe plants.
Pests and Diseases
NC State lists crown rot, powdery mildew and verticillium wilt as problems, and notes monkshood is deer and rabbit resistant. The RHS adds that it can be affected by aphids and fungal stem rot. Good drainage, spacing for airflow and watering at the base help prevent most of these. Remove and bag infected stems rather than composting them.
Frequently Asked Questions
How do you grow monkshood?
Plant the tuberous roots in fall or spring with the crowns just below the soil surface, in humus-rich, moist but well-drained soil with partial or afternoon shade. Keep the soil evenly moist and wear gloves whenever you handle the plant.
Is monkshood poisonous to touch?
The RHS advises avoiding skin contact and wearing gloves, and NC State recommends gloves when handling it. Every part of the plant contains toxic alkaloids, so wash your hands and tools after any contact.
When does monkshood bloom?
In mid to late summer, according to the RHS, and as late as September to October in places like Illinois, according to Illinois Extension. Cutting back after flowering can encourage more blooms.
Does monkshood spread?
Slowly. It is a clump-forming perennial with a slow growth rate, so it widens gradually and may self-seed. Remove faded flower spikes to limit seedlings.
Can monkshood grow in full sun?
Only where summers are cool and the soil stays moist. The RHS says it tolerates full sun if the soil is humus-rich and mulched; in warmer areas NC State recommends protection from afternoon sun.
What should I do if my pet eats monkshood?
Call your veterinarian or the ASPCA Animal Poison Control Center at (888) 426-4435 immediately. NC State notes monkshood may be fatal to pets, so don’t wait for symptoms.