Herb · Asteraceae
Wormwood
Artemisia absinthium
Hand it poor, dry soil and full sun, and this silvery bitter herb pretty much takes care of itself.
Full sun
Every 10–21 days
90–120 days
USDA 4–9
Overview
So what is wormwood? It's a tough, silver-leaved perennial in the daisy family, with finely cut foliage and a sharp bitterness you won't mistake for anything else. It ran wild across Europe and Asia long before it made its way to North America, where it's since spread on its own. And most folks grow it for that aromatic gray foliage, not the small, dull yellow flowers it puts out in late summer.
Here's the good news: it barely asks for anything. Lean, dry, sharply drained soil and a sunny spot are all it really wants, and rich ground or soggy roots are what get it into trouble. It shrugs off drought and poor soil that would sink pickier plants, and it's just as happy through a bitter winter as it is in real summer heat.
There's a catch, though. Every part of wormwood holds thujone, a neurotoxin, plus the bitter compound absinthin that absinthe is named after. That bitterness keeps most animals from bothering with it, but it isn't something you'd want to chew on, and its roots and rain-washed leaves can hold back whatever's growing nearby. So give it a little space of its own, okay?
Care
The short version: full sun and lean, dry, sharply drained soil are what it wants. Water it sparingly and only once the ground's dried out, forget the fertilizer, and give it a shear after it blooms so it doesn't flop over.
Light
Wormwood's a full sun plant, plain and simple. It'll put up with a bit of partial shade, but give it too much and you'll get weak, leggy stems that flop open by midsummer, so pick the brightest spot you've got.
Water
Less really is more here. Let the soil dry out completely between drinks, watering only every 10 to 21 days once it's established, and never leave the ground wet. That standing moisture? It's the one thing that reliably kills it, through root rot.
Soil
Give it poor to moderately fertile, dry, sharply drained ground, sandy or loamy, and it's happy. It handles a wide pH range, anywhere from 5.5 to 8.0, and it actually does better lean than rich, so don't bother improving the bed.
Temperature
This is a genuinely tough customer, comfortable anywhere from -22°F to 95°F (-30°C to 35°C). That cold hardiness gets it through brutal winters no problem, and it takes real summer heat in stride too.
Humidity
It likes things on the dry side, around 30% to 50% humidity, which fits its drought-tolerant streak. Damp, muggy air does it no favors, since all that trapped moisture just invites the foliage to fade.
Feeding
You can pretty much skip feeding altogether. Wormwood thrives in poor soil, and the most it wants is a light topdressing of compost in spring. Feed it too richly and all you get is soft, floppy growth.
Pruning
Pinch the stems back in late spring so it doesn't get leggy. Once it's flowered, shear it by up to half to bring back fresh, compact foliage, and deadhead promptly so it doesn't seed itself all over the place.
Repotting
Wormwood hardly ever gets grown in a pot, but if yours is, repot every 2 to 3 years in spring. Roots circling the pot, water running straight through, sparse new growth? Those are your cues it's outgrown its home.
Size & spacing
A grown plant hits 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 standing.
When to plant
Wormwood keeps to the seasons like any cold-hardy perennial, so timing's easy. Start seed indoors in early spring, move the young plants out after the last frost once the soil's warmed up, and watch for those small yellow flowers from August into September while you snip aromatic foliage all 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
Here's the funny thing about wormwood: most of its problems come from too much fuss, not too little. Wet soil, rich ground, and shade cause way more grief than a dry spell ever will. See something off? Match it below and jump on it early, before a floppy or rotting plant heads downhill.
A wilting plant with black, mushy roots
Nothing kills wormwood faster than wet feet, and this is root rot, brought on by soil that stays soggy and drains too slowly. Once the roots go dark and soft, there's really no saving it, so lift the plant, toss it, sort out the drainage, and quit watering the spot.
Fix:
- Improve drainage and stop watering
- Remove and discard affected plants
Stems flopping open from the middle in summer
That's summer flop, and it usually means too much water, too rich a soil, or not enough sun. Rich ground and wet weather push soft, top-heavy growth that just can't hold itself up. So shear the plant back by up to half after it blooms, and pinch the stems in late spring before the flopping even 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 bugs
Even a bitter, aromatic plant like wormwood can pull in aphids on its soft new growth. Look for the little clustered bugs and the sticky honeydew they leave behind. A hard jet of water knocks most of them off, and you only need insecticidal soap if they keep coming back.
Fix:
- Dislodge with a strong spray of water
- Treat with insecticidal soap if persistent
Toxicity
This one's worth keeping away from pets, grazing animals, and anyone tempted to snack on it. Every part carries thujone, a neurotoxin that can bring on vomiting, tremors, and seizures if enough gets eaten. The intense bitterness puts most animals off after a taste, but why risk it? 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 will usually drool and throw up, and diarrhea often isn't far behind. The real worry's the thujone, though, which can bring on tremors and seizures if a cat eats much of it.
Dogs Toxic
Most dogs that bite the bitter foliage just end up with an upset stomach, vomiting, or loose stools. But let one eat enough and the thujone turns serious, with muscle tremors and seizures.
Horses Toxic
Horses can get colic and a dull, off mood from grazing it, and a big feed risks the tremors and convulsions that come with thujone poisoning.
Rabbits Toxic
Don't let rabbits nibble it. The same thujone that troubles other animals upsets their gut and, in any real amount, goes after the nervous system.
Livestock Toxic
Cattle, sheep, and goats usually leave the bitter plant alone, but a hungry animal on poor pasture can take in enough thujone to end up with stomach pain and nervous twitching.
Birds Toxic
Keep wormwood away from birds, since those volatile oils and thujone are just too strong for their little bodies to handle safely.
People Caution
Sure, wormwood flavors absinthe and bitter tonics, but it's no 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 people just grow the plain species, and that's fine, but a couple of selections are worth a look for their foliage and neater shape.
'Lambrook Silver'
A neater, more compact pick that's loved for its finely cut, silvery-gray leaves.
Artemisia 'Powis Castle'
A vigorous silver-leaved cross of A. absinthium and A. arborescens that barely flowers and gets 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
Want more wormwood? It's easy to multiply. You can raise it slowly from its tiny seed, or take the quick route and split a clump or root 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 just scatter them on the surface and leave them uncovered, and they'll come up in 2 to 3 weeks. It 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 an old clump is the fastest way to freshen up a tired plant. Lift and divide it 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 easily, rooting in about 3 to 4 weeks.
Myths
The thujone in wormwood makes absinthe a hallucinogen.
That hallucinogen story? It doesn't hold up. Both old pre-ban absinthe and the modern stuff carry way too little thujone to do anything to your mind, and you'd hit alcohol poisoning long before the thujone added up to a neuroactive dose. Absinthe's effects come from the alcohol, not the herb.
Wormwood's a natural herb, so it's safe to take freely.
Natural doesn't 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. There's a reason US law caps how much thujone is allowed in food and drink.
Planting wormwood makes nearby vegetables healthier.
It usually does the opposite, believe it or not. Wormwood is allelopathic, releasing a water-soluble compound called absinthin from its roots and from foliage that rain washes off. That absinthin stunts the plants growing close to it, so wormwood tends to suppress its neighbors instead of helping them.