Wormwood (Artemisia absinthium)
Wormwood is a feathery herbaceous perennial native to temperate Eurasia and North Africa that has naturalized in North America. It has a long, interesting history of use as a bitter flavoring for alcoholic drinks and medicinal treatment for a wide number of ailments.
Wormwood is an attractive plant in the Daisy family (Asteraceae) with deeply lobed, silvery gray-green leaves with a fragrance of garden sage and small, yellow flowers blooming in the late summer. It grows to 3' tall and 2' wide and is sometimes grown as an ornamental for borders, rock gardens, and containers.
Its main uses, though, are medicinal and as a flavoring. Wormwood has antifungal, anti-inflammatory, and antimicrobial properties. It is used to stimulate digestion and for loss of appetite, as an antidepressant, and to treat arthritis and Crohn's disease. It gets its name, Wormwood, from its use to treat parasitic worms and is being studied as a potential bio-insecticide.
Wormwood is well-known as the anise or licorice flavoring in vermouth and green absinthe liquor. However, oils in the foliage contain thujone that can cause seizures and neural damage if ingested in large quantities. Before the amount of thujone was regulated in the liquor industry, absinthe was banned in the United States and some European, African, and South American countries for most of the 20th century because it was thought to be hallucinogenic and poisonous. It is now legally available in the United States since the ban was lifted in 2007 with a limit on the amount of thujone allowed.
Wormwood grows best in full sun in average, excellent draining soil. It will readily self-seed, so it is well to deadhead the flowers to prevent it from spreading. It is hardy in USDA zones 4+
How to Grow Wormwood Plants
Climate and Soil Requirements
- Climate: Wormwood thrives in temperate climates and is best suited for USDA hardiness zones 4-9. The plant prefers cooler summers and can tolerate a range of temperatures but is sensitive to extreme heat and humidity.
- Soil: Prefers well-draining, sandy or loamy soil with a slightly alkaline to neutral pH (7.0-8.5). Wormwood can tolerate poor soil conditions but performs best in nutrient-rich soil.
Planting
- Location: Choose a sunny location that receives at least 6-8 hours of direct sunlight daily. Wormwood can tolerate partial shade but may become leggy if not exposed to enough light.
- Soil Preparation: Prepare the soil by tilling and adding sand or grit to improve drainage if necessary. Wormwood does not require rich soil and can thrive in relatively poor, well-drained soil.
- Planting Time: Plant seeds or young plants in the spring after the last frost. If starting from seed, sow seeds indoors 8-10 weeks before the last frost and transplant seedlings outdoors once they are sturdy.
- Spacing: Space plants 18-24 inches apart to allow adequate room for growth and air circulation.
Watering
- Establishment Phase: Water regularly to keep the soil consistently moist but not waterlogged during the first year. Consistent moisture is crucial for young plants.
- Mature Plants: Once established, Wormwood is drought-tolerant. Water deeply and infrequently, allowing the top inch of soil to dry out between waterings. Avoid overwatering, as Wormwood prefers dry conditions.
Sunlight
- Full Sun: Ensure the plants receive at least 6-8 hours of direct sunlight daily for optimal growth and robust foliage.
Fertilizing
- Minimal Fertilization: Wormwood thrives in poor soil and does not require heavy fertilization. Apply a light, balanced fertilizer in early spring if the soil is particularly poor.
- Frequency: Fertilize sparingly, as too much fertilizer can reduce the plant's aromatic oils and bitterness.
Pruning and Maintenance
- Routine Pruning: Prune in early spring to remove dead or damaged stems and to shape the plant. Light pruning throughout the growing season encourages bushier growth and prevents the plant from becoming leggy.
- Maintenance: Wormwood requires minimal maintenance once established. Mulch around the base to retain moisture and suppress weeds.
Pest and Disease Management
- Common Pests: Wormwood is generally pest-resistant but can occasionally attract aphids and spider mites. Use insecticidal soap or neem oil to control infestations.
- Diseases: Watch for signs of fungal diseases such as root rot and powdery mildew. Ensure proper spacing, good air circulation, and avoid overhead watering to reduce disease risk. Apply fungicides if necessary.
Harvesting Leaves
- When to Harvest: Harvest leaves as needed throughout the growing season. The best time to harvest is in the morning after the dew has dried, when the essential oils are most concentrated.
- How to Harvest: Use scissors or garden shears to cut the leaves, taking care not to damage the main stems. Harvesting regularly encourages new growth and maintains the plant's shape.
