PL. —Artemisia annuaBotanical illustration — drop image

Sweet Annie

SpringSummerFallInvasive

3a–10bHardiness zone

Background

Artemisia annua is a fast-growing annual herb native to temperate Asia, now naturalized across much of the world. It reaches 4–8 feet in a single season, forming dense, feathery mounds of finely cut, intensely aromatic bright green foliage. Gardeners grow it primarily for its dried stems, which hold fragrance and form well into winter and are widely used in wreaths and arrangements.

It thrives in full sun and tolerates poor, dry soils. Excessive fertility or moisture produces lush but less fragrant growth. It self-sows prolifically; remove seed heads before they disperse unless reseeding is welcome — it can colonize bare ground aggressively. Lean soil and good air circulation produce the most aromatic plants and reduce disease pressure.

The plant contains artemisinin, a sesquiterpene lactone that became the basis for artemisinin-combination therapies (ACTs), now the primary treatment for malaria worldwide. Tu Youyou received the 2015 Nobel Prize in Physiology or Medicine for this discovery. In traditional Chinese medicine, the dried herb — known as qinghao — has been used for centuries to reduce fever, including malarial fever.

Good companions

Calendula Yarrow Marigold Sunflower

Keep apart

Bronze Fennel

Care guide

SunFull sun

WaterLow

SoilWell-drained, dry to average, lean to average fertility

Spacing24–36 in

Height4–8 ft

Zone3a – 10b

Direct sowInvasive

Seasonal tasks

spring

cutThin or transplant seedlings to 24–36 inches apart once they reach 3–4 inches tall to ensure air circulation and prevent overcrowding.

watchCheck seedlings for damping off during wet or cool springs. If stems collapse at the soil line, reduce watering, improve drainage, and remove affected plants promptly.

sowStart seeds indoors 6–8 weeks before last frost. Press seeds onto the surface of moist potting mix — they need light to germinate. Do not cover with soil.

sowDirect sow on the soil surface after last frost. Tamp lightly to ensure seed contact but leave exposed to light.

summer

cutHarvest stems for drying in late summer when plants are in early bud and fragrance peaks. Cut long stems, bundle loosely, and hang upside down in a dry, well-ventilated space out of direct light.

fall

watchMonitor seed heads in early fall. Cut and bag stems before seeds fully ripen and disperse if naturalizing is not desired.

Common problems

Powdery mildew

Symptoms

White or grey powdery coating on leaves — usually starting on older growth in humid conditions or when nights cool.

Treatment

Improve air circulation by thinning plants. Apply neem oil or potassium bicarbonate spray at first sign. Avoid overhead watering.

Damping Off

Symptoms

Seedlings collapse at the soil line with thin, water-soaked stems; seeds may fail to emerge or rot before sprouting.

Treatment

Sow in well-draining mix, avoid overwatering, and ensure good airflow. Remove affected seedlings and let the surface dry between waterings.

Root rot

Symptoms

Plants wilt, yellow, and stunt even in moist soil; lower stems and roots turn brown, soft, and mushy and the plant may collapse. Most common in heavy, wet, or poorly drained ground.

Treatment

Improve drainage and stop overwatering, and never plant too deep. Lift and destroy badly affected plants along with the soil around the roots. Grow in raised or free-draining beds to prevent it returning.