Threadleaf Wormwood Plant Care

Threadleaf Wormwood (Artemisia filifolia) belongs to the Asteraceae family within the Artemisia genus. Threadleaf Wormwood is native to North America. Threadleaf Wormwood is also known as Silvery Wormwood, Prairie Sage, Artemisia plattensis.

Threadleaf Wormwood displays an upright, bushy shrub growth habit, reaching up to 2 ft tall with a spread of approximately 3 ft. Threadleaf Wormwood produces insignificant small yellow or white flowers.

Leaf size: approximately 2 inches.

Water a young or newly planted Threadleaf Wormwood every 7–14 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established shrubs mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Threadleaf Wormwood thrives in full sun to partial shade.

Artemisia filifolia tolerates temperatures of 50–75°F. Threadleaf Wormwood prefers humidity levels of 30–60%.

Well-draining sandy soil with low fertility. Good drainage is essential for Threadleaf Wormwood to prevent waterlogging, which leads to root rot and fungal issues.

Feed Threadleaf Wormwood every 6 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established shrubs in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with full sun to partial shade and well-draining sandy soil with low fertility. Avoid low spots where water collects after rain.

Threadleaf Wormwood is suited to USDA Zone 4a – 9b.

Plant container-grown or balled-and-burlapped shrubs in spring or early autumn, setting the root flare at soil level, and water well after planting.

Threadleaf Wormwood can spread to about 3 ft (0.9 m) and reach about 2 ft (1 m) tall. Space plants about 3 ft (0.9 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the plant spacing calculator.

Prune Threadleaf Wormwood while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the shrub in one year.

Threadleaf Wormwood is hardy down to USDA zone 4a, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown shrubs need extra protection: roots in a pot freeze much more easily than roots in the ground.

Threadleaf Wormwood can be propagated through seeds, division. Similar propagation techniques also apply to southernwood plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Threadleaf Wormwood is susceptible to aphids, spider mites. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

Threadleaf Wormwood grows outdoors in USDA Zone 4a – 9b. It survives winters down to planting zone 4a. Threadleaf Wormwood is native to North America.