Wormwood

Wormwood: how do you recognise it?

Habit

Subshrub with a woody base and upright stems, 60–90 cm tall and about 60 cm wide.

Leaves

Two to three times divided, 5–10 cm, silver-grey and silky, strongly aromatic.

Flowers

Small, rounded, pale yellow heads in loose panicles from July to September. They are wind-pollinated.

Scent and taste

Strongly herby and slightly camphor-like; the leaves are very bitter.

Roots

A deep, woody rootstock that helps it cope with drought.

Flowering: July–September · Plants: April–May and September · Pruning: April

Why grow it?

• Silver-grey, finely cut foliage from spring to autumn: a point of light among green plants.
• Excellent drought tolerance: ideal for a gravel garden or a dry, sunny border.
• The leaves release a strong, herby scent when you brush against them.
• Silver foliage ties colours together: purple, blue and pink look even better beside it.
• Dried stems look good in dried arrangements and were once put in sachets among woollens.

Wormwood: where does it grow best?

• Full sun: in shade it becomes floppy and less silvery.
• Poor, well-drained soil: sand, loam or clay, neutral to chalky. On heavy clay, mix in grit or coarse sand.
• Dry: wet feet in winter are its worst enemy.
• Allow 50–60 cm between plants.

Light

Sun

Soil type

Sand, loam or clay

Acidity

Neutral or chalky

Moisture

Dry

Size

0.9 m tall, 0.6 m wide

Hardiness

Hardy (to -30 °C)

Goes well with

• Lavender: Likes the same dry, sunny, chalky spot.
• Catmint: Lavender-blue flowers that stand out well against the silver foliage.
• Balkan clary: Purple spikes in summer, for the same dry soil.
• Mullein: Tall yellow flower spikes above the silver-grey leaves in a gravel garden.
• Feather grass: Fine, swaying plumes that move beautifully beside the silver clump.

Wormwood: when and how to plant it?

Plant in April–May and September.

1. Plant in April–May or in September, so the roots can establish before winter.
2. Dig a hole slightly larger than the pot. On heavy soil, mix in coarse sand or grit, but no compost or manure.
3. Set the plant at the same depth as it was in the pot and firm the soil well.
4. Keep 50–60 cm between it and other plants.
5. Water well once, then only in severe drought until it is established.
6. Mulch with gravel or grit rather than compost: this keeps the base dry.

Care

Watering

Once established it hardly ever needs water, even in dry summers. Too much water makes it floppy and prone to rot.

Feeding

Do not feed: on rich soil it grows too lush and falls open.

Spent flowers

The flower panicles are not very decorative. Cut them off if you mainly want the silver foliage and to limit self-seeding.

Harvesting

In July, before flowering, cut a few stems and hang them in bunches to dry for dried arrangements. Wear gloves if you have sensitive skin.

Renewing

After 4–5 years plants become woody and bare at the base. Replace them with a young plant raised from a cutting.

Tip: Give wormwood a dry, sunny spot and never feed or water it extra: the poorer the soil, the more silvery and compact the plant. Cut it back every spring to just above the new shoots.

Wormwood: when to prune it?

Pruning months: April.

When: In April, as soon as you see new shoots appearing at the base.

How:

• Cut last year’s stems back to 15–20 cm above the ground, just above new shoots.
• Do not cut into bare old wood without buds: it regrows poorly from there.
• In summer, remove spent flower panicles for a compact, silver plant.
• Do not prune in autumn: the old stems protect the base in winter.

Caution: Wear gloves when pruning if you have sensitive skin and wash your hands afterwards. Do not leave prunings where children or animals can reach them.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In July–August take semi-ripe cuttings of 8–10 cm, preferably with a heel. Root them in a slightly moist mix of potting compost and sand.

Division

In April, split an older clump into pieces, each with roots and young shoots, and replant them straight away.

Wormwood: how does it get through the winter?

Hardy to −30 °C.

• Very hardy, to about −30 °C: frost is not a problem.
• Wet soil in winter is a danger, though: choose a dry, well-drained spot.
• Leave the stems standing over winter and do not prune until April.
• Stand a plant in a pot under cover, out of heavy rain.

Diseases and pests

• Root rot: The plant yellows and dies in winter or after a wet spell. Plant in a dry, well-drained spot and do not give extra water.
• Floppy and bare: In shade or on rich soil the plant falls open and goes bare at the base. Grow it in full sun on poor soil and prune every spring.
• Aphids: Black or green aphids on the shoot tips in early summer. Hose them off or cut off the tips.
• Self-seeding: It occasionally seeds itself into gravel or between paving. Cut off spent panicles before the seed ripens.

Through the year

• April: Cut back to 15–20 cm. Plant or divide.
• May: Plant. New silver growth.
• June: Watch for aphids. No watering needed.
• July: Flowering begins. Cut stems for drying. Take cuttings.
• August: Flowering. Take cuttings. Remove spent panicles.
• September: Last flowers. Plant.
• October: Leave the stems standing for winter.
• November: Rest. Make sure the base stays dry.

Edible and useful

Not edible. Wormwood contains thujone, which in larger amounts causes convulsions and damages the nervous system and kidneys. Do not make your own tea, liqueur or absinthe from it; certainly not during pregnancy and not for children. Also poisonous to pets. In the garden it is a lovely silver-grey plant that deters some insects. If any is swallowed, call a poison centre (in Belgium 070 245 245) or your doctor at once.

Did you know?

• The drink absinthe is named after this plant, and the word vermouth comes from Wermut, the German name for wormwood.
• Wormwood is wind-pollinated, which is why its flowers are small and inconspicuous, without bright colours to attract insects.
• The cultivar ‘Lambrook Silver’ is named after East Lambrook Manor, the garden of the English garden writer Margery Fish.