Herb · Asteraceae
Wormwood
Artemisia absinthium
Give it poor, dry soil and full sun, and this silver-leaved bitter herb all but grows itself.
Full sun
Every 10–21 days
90–120 days
USDA 4–9
Overview
Wormwood is a hardy, silver-leaved perennial herb from the daisy family, known for its finely cut foliage and its sharp, unmistakable bitterness. It grew wild across Europe and Asia long before it crossed to North America, where it has since spread on its own. Most gardeners grow it for the aromatic gray foliage rather than the small, dull yellow flowers it carries in late summer.
It asks for almost nothing. Lean, dry, sharply drained soil and a spot in full sun suit it perfectly, and rich ground or wet feet only cause trouble. Hardy from a deep winter chill up to real summer heat, it shrugs off drought and poor soil that would defeat fussier plants.
The same chemistry that makes wormwood famous also makes it a plant to handle with care. Every part holds thujone, a neurotoxin, along with the bitter compound absinthin that gives absinthe its name. That bitterness keeps most animals from eating it, but it isn't a herb to chew freely, and its roots and rain-washed leaves can stunt the plants growing nearby.
Care
The short version: full sun and lean, dry, sharply drained soil. Water sparingly and only once the ground has dried out, skip the fertilizer, and shear the plant back after it blooms to keep it from flopping.
Light
Wormwood wants full sun and the lean, open conditions that come with it. It will tolerate a little partial shade, but too much shade gives you weak, leggy stems that flop open by midsummer.
Water
Less is more here. Let the soil dry out completely between drinks, watering only every 10 to 21 days once the plant is established, and never leave the ground wet. Standing moisture is the one thing that reliably kills it, through root rot.
Soil
Give it poor to moderately fertile, dry, sharply drained ground, sandy or loamy. It handles a wide pH range, anywhere from 5.5 to 8.0, and actually grows better in lean soil than in rich, so don't bother improving the bed.
Temperature
This is a genuinely tough plant, comfortable from about -22°F to 95°F (-30°C to 35°C). That cold hardiness lets it sail through hard winters, and it stands up to real summer heat as well.
Humidity
It prefers things on the dry side, around 30% to 50% humidity, in keeping with its drought-tolerant nature. Damp, muggy air does it no favors, since trapped moisture invites the foliage to decline.
Feeding
Skip the feeding almost entirely. Wormwood thrives in poor soil, and the most it needs is a light topdressing of compost in spring. Rich feeding only pushes soft, floppy growth.
Pruning
Pinch the stems back in late spring to keep the plant from getting leggy. After it flowers, shear it by up to half to bring back fresh, compact foliage, and deadhead promptly so it doesn't self-seed all over the garden.
Repotting
Wormwood is rarely grown in a pot, but if yours is, repot every 2 to 3 years in spring. Watch for roots circling the pot, water running straight through, and sparse new growth, all signs it's outgrown its container.
Size & spacing
A mature plant reaches about 2 to 4 feet (60 to 120 cm) tall and spreads 18 to 35 inches (45 to 90 cm) wide. Give it that much room so air moves freely around the foliage and the stems stay upright.
When to plant
Wormwood follows the seasons of a cold-hardy perennial. Start seed indoors in early spring, set young plants out after the last frost once the soil has warmed, and expect the small yellow flowers from August into September while you harvest the aromatic foliage through summer.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Early spring, 6-8 weeks before last frost; surface sow as seed needs light
- Plant: After the last spring frost, once soil has warmed
- Harvest: Yellowish flowers August to September; harvest aromatic foliage in summer at or just before bloom
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Wormwood is tough, and most of its troubles come from too much kindness rather than neglect. Wet soil, rich ground, and shade cause far more harm than drought ever will. Match what you see below and act before a floppy or rotting plant goes downhill.
Wilting plant with black, mushy roots
Wet feet kill wormwood faster than anything else. This is root rot, set off by soil that stays soggy and drains too slowly. There's no saving a plant once the roots turn dark and soft, so lift it, bin it, fix the drainage, and stop watering the area.
Fix:
- Improve drainage and stop watering
- Remove and discard affected plants
Stems splaying open from the center in summer
This is summer flop, and it usually means the plant has too much water, too rich a soil, or too little sun. Rich ground and wet weather push soft, top-heavy growth that can't hold itself up. Shear the plant back by up to half after it blooms, and pinch the stems in late spring before the flopping starts.
Fix:
- Shear plants back by up to half after bloom to force fresh compact growth
- Pinch stems in late spring before flopping starts
Curled shoot tips crawling with tiny insects
Even a bitter, aromatic plant like wormwood can draw aphids onto its soft new growth. Look for the small clustered insects and the sticky honeydew they leave behind. Knock them off with a hard jet of water, and reach for insecticidal soap only if they keep coming back.
Fix:
- Dislodge with a strong spray of water
- Treat with insecticidal soap if persistent
Toxicity
This is a plant to keep away from pets, grazing animals, and casual snacking. Every part holds thujone, a neurotoxin that can cause vomiting, tremors, and seizures when eaten in quantity. The intense bitterness keeps most animals from taking more than a taste, but don't count on it, and don't treat wormwood as something safe to eat.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Toxic
A cat that chews the leaves usually drools and throws up, often with diarrhea soon after. The real danger is the thujone, which can bring on tremors and seizures if a cat eats much.
Dogs Toxic
Most dogs that bite the bitter foliage end up with an upset stomach, vomiting, or loose stools. Eat enough and the thujone turns serious, with muscle tremors and seizures.
Horses Toxic
Horses can suffer colic and a dull, off mood from grazing the plant, and a large feed risks the tremors and convulsions that follow thujone poisoning.
Rabbits Toxic
Don't let rabbits nibble it. The same thujone that troubles other animals upsets their gut and, in quantity, attacks the nervous system.
Livestock Toxic
Cattle, sheep, and goats normally leave the bitter plant alone, but a hungry animal on poor pasture can take in enough thujone to cause stomach pain and nervous twitching.
Birds Toxic
Keep wormwood away from birds, since the volatile oils and thujone are too strong for their small bodies to handle safely.
People Caution
Wormwood flavors absinthe and bitter tonics, but it isn't a salad green. The thujone it carries can cause vomiting, tremors, and seizures if you eat the plant freely, so treat it as a flavoring to use sparingly, never a food.
Foliage is strongly aromatic and bitter; volatile oils can irritate the skin of sensitive people, so wear gloves when pruning or harvesting in quantity.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Most gardeners grow the straight species, but a couple of selections stand out for their foliage and tidier shape.
'Lambrook Silver'
A neater, more compact selection prized for its finely cut, silvery-gray leaves.
Artemisia 'Powis Castle'
A vigorous silver-leaved hybrid of A. absinthium and A. arborescens that rarely flowers and is grown purely for its mound of foliage.
Companions
Plant near
carrots: Used traditionally as a strongly scented distant border to help mask the scent of carrots from pests; keep well away from the roots to avoid allelopathic suppression.
Keep apart
fennel: Volatiles and root-exuded absinthin from wormwood inhibit fennel germination and growth.
sage: Absinthin washed from wormwood foliage by rain stunts nearby herbs such as sage.
anise: Aromatic seed herbs near wormwood suffer reduced germination and stunting from absinthin.
How to propagate
Wormwood is easy to multiply, whether you raise it slowly from its tiny seed or take a faster shortcut by splitting a clump or rooting a cutting.
SeedModerate
Early spring, 6-8 weeks before last frost · Germinates in 2-3 weeks; reaches usable size in the first to second year
Start seed indoors about 6 to 8 weeks before your last frost. The seeds are tiny and need light to sprout, so scatter them on the surface and leave them uncovered, and they break ground in 2 to 3 weeks. The plant takes its time, filling out to a usable size over the first or second year, and once it's settled outdoors it self-sows freely.
DivisionEasy
Spring or early fall · Roots in a few weeks and re-establishes the same season
Splitting old clumps is the quickest way to rejuvenate a tired plant. Lift and divide in spring or early fall every 2 to 3 years, and the new pieces root within a few weeks and settle back in the same season.
Stem cuttingsEasy
Late spring to summer from softwood or semi-ripe shoots · Roots in about 3-4 weeks
From late spring through summer, take 8 to 10 cm tip cuttings from softwood or semi-ripe shoots. Push them into a gritty, sharply drained mix and they strike readily, rooting in about 3 to 4 weeks.
Myths
The thujone in wormwood makes absinthe a hallucinogen.
The hallucinogenic reputation doesn't hold up. Both old pre-ban absinthe and the modern stuff carry far too little thujone to do anything to the mind, and a drinker would hit alcohol poisoning long before the thujone added up to a neuroactive dose. The effects of absinthe come from the alcohol, not the herb.
Wormwood is a natural herb, so it's safe to take freely.
Natural does not mean harmless here. Every part of the plant holds thujone, a neurotoxin, and taking large or repeated doses of wormwood preparations can damage the nervous system. The amount of thujone allowed in food and drink is capped by US law for good reason.
Planting wormwood improves the health of nearby vegetables.
It usually does the opposite. Wormwood is allelopathic, releasing a water-soluble compound called absinthin from its roots and from foliage washed by rain. That absinthin stunts the plants growing close to it, so wormwood tends to suppress its neighbors rather than help them.