Why Are My Artemisia Leaves Curling?

Overwatering and root rot

Artemisia species originate from dry, often impoverished habitats across Europe, Asia, and North America, and are adapted to survive on very little water once established. In UK gardens, overwatering is the most common mistake made with artemisia, particularly with container-grown plants. Roots kept in persistently wet compost rot quickly, and once the root system is compromised the plant can no longer take up water or nutrients. The silvery leaves begin to curl, discolour, and the plant may collapse even when the soil is wet.

A container-grown artemisia that has been watered on a regular schedule regardless of the compost moisture is the most typical victim. In the ground, overwatering is rarely a problem in typical UK conditions unless the plant is additionally situated in a low-lying wet spot.

What to do

• Allow the compost to dry out completely between waterings for container-grown plants. In the garden, established artemisia usually needs no supplementary watering from mid-spring onwards once rain is providing adequate moisture.
• If root rot is suspected, remove the plant from its pot, cut away any darkened or mushy roots, and repot into fresh, very gritty, free-draining compost.
• Use a terracotta pot for artemisia grown in containers, as the porous walls allow excess moisture to evaporate more quickly than plastic.

Poor drainage

Even without overwatering, artemisia planted in heavy clay soil or in a position where water pools after rain will struggle. Clay retains water for far longer than artemisia's roots can tolerate, and in a wet UK winter this can be enough to cause root damage, leaf curling, and plant death even without any additional watering. Yellowing or browning at the stem base where it meets the soil, alongside curling upper leaves, is a typical presentation of waterlogged roots.

What to do

• Improve drainage before planting by digging generous quantities of horticultural grit and coarse sand into the soil. A ratio of one part grit to three parts soil makes a significant difference in heavy clay.
• Plant on a slight mound raised 10 to 15 cm above the surrounding soil level to ensure water drains away from the crown.
• In persistently wet soil, consider growing artemisia in a raised bed or large container where drainage can be fully controlled.

Too much shade

Artemisia is a full-sun plant. In partial or heavy shade, it produces lush, soft, green-tinged growth rather than the compact, intensely silver foliage it is grown for. Shaded stems become long, lax, and floppy, the leaves may curl or twist as they grow unevenly, and the plant is far more prone to fungal problems because the dense, weak growth holds moisture and restricts air circulation.

A position that receives at least six hours of direct sun per day produces the best artemisia foliage. South and west-facing borders are ideal in the UK.

What to do

• Transplant to a sunnier position if possible, ideally in early autumn or early spring.
• Cut back lax, shaded growth hard in spring to encourage compact, well-branched new growth from the base. Most artemisia species and cultivars respond well to cutting back to about 10 to 15 cm.
• Avoid enriching the soil with compost or fertiliser: lean soil combined with full sun produces the most silvery, compact, and attractive foliage.

Aphid infestation

Although artemisia is reasonably pest-resistant, aphid colonies occasionally establish on new growth and shoot tips, causing the leaves to curl, pucker, and distort. Colonies are most common in spring when new growth is soft and palatable. Aphids on artemisia are often greenish and well-camouflaged against the young growth, so look closely at curled shoot tips for moving insects or honeydew residue.

What to do

• Knock aphid colonies off with a strong jet of water from a hose, or rub them away with a gloved hand.
• For persistent infestations, spray with insecticidal soap, concentrating on the undersides of leaves and curled shoot tips.
• Artemisia contains aromatic compounds that deter many insects, so heavy aphid problems are unusual: if they recur repeatedly, check that the plant is receiving enough sun and not growing too lush and soft, as weak growth is more attractive to pests.

Rust disease

Rust is an occasional problem on artemisia, particularly in wet summers. Infected leaves develop bright orange or rusty brown pustules on the undersides, and the upper surface of the affected leaves puckers, discolours, and may curl upward. Rust is a fungal disease that spreads by spores and is most active in humid conditions with poor air circulation.

What to do

• Remove and dispose of affected leaves promptly in the bin (not the compost heap) to reduce spore spread.
• Improve air circulation by thinning any crowded plants around the artemisia and cutting back the plant itself if it has become dense.
• Avoid watering overhead: direct water at the root zone to keep the foliage dry.
• A sulphur-based fungicide approved for ornamental use can help control an active rust outbreak. Check the label for suitability on artemisia before applying.

Frequently asked questions

Why are my artemisia leaves curling?

Artemisia leaves curl most often because of overwatering or poor soil drainage. Artemisia is adapted to dry, free-draining soils and is highly susceptible to root rot in wet conditions. Too much shade is another common cause: without enough light, the stems become lax and the silvery foliage loses its quality.

How often should I water artemisia?

Once established, most artemisia species need very little supplementary watering. In average UK conditions they are largely self-sufficient on rainfall. Water newly planted specimens weekly for the first season, then leave them to fend for themselves. In pots, water only when the compost has dried out completely.

Why is my artemisia going floppy and losing its silver colour?

Floppy, green-tinged growth rather than the characteristic silver is almost always caused by too much shade or too much nitrogen-rich soil. Artemisia needs full sun and lean, well-drained soil to produce its compact, intensely silver foliage. In rich, moist soil or partial shade it produces lush, floppy growth that is more susceptible to rot.

Does artemisia spread?

This depends on the species. Artemisia absinthium (wormwood) and A. vulgaris (mugwort) can spread vigorously by underground rhizomes and self-seeding. More compact cultivars like A. 'Powis Castle' are clump-forming and do not spread invasively. Check the growth habit of your specific variety before planting.