Korean Arborvitae Plant Care

Korean Arborvitae (Thuja koraiensis) belongs to the Cupressaceae family within the Thuja genus. Korean Arborvitae is native to Korea and the extreme northeast of China (Changbaishan).

Korean Arborvitae displays a pyramidal, columnar growth habit, reaching up to 40 ft tall with a spread of approximately 15 ft. Korean Arborvitae produces small cones, not showy.

Leaf size: approximately 0.5 inches.

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

Korean Arborvitae thrives in full sun to part shade.

Thuja koraiensis tolerates temperatures of 10–100°F. Korean Arborvitae prefers humidity levels of 30–70%.

Well-draining loamy soil with good aeration. Good drainage is essential for Korean Arborvitae to prevent waterlogging, which leads to root rot and fungal issues.

Feed Korean Arborvitae every 8 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established trees 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 part shade and well-draining loamy soil with good aeration. Avoid low spots where water collects after rain.

Korean Arborvitae is suited to USDA Zone 5a – 7b.

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

Korean Arborvitae can spread to about 15 ft (4.6 m) and reach about 40 ft (12 m) tall. Space plants about 15 ft (4.6 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 tree spacing calculator.

Prune Korean Arborvitae 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 tree in one year.

Korean Arborvitae is hardy down to USDA zone 5a, so once established it can stay outdoors through winter in that zone and warmer ones.

Water deeply in late autumn before the ground freezes — evergreens keep losing water through their needles all winter, 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 trees need extra protection: roots in a pot freeze much more easily than roots in the ground.

Korean Arborvitae can be propagated through seeds, cuttings. Similar propagation techniques also apply to arborvitae plant care, which shares the same genus.

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

Korean Arborvitae is susceptible to spider mites, bagworms, scale insects. 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.

Korean Arborvitae grows outdoors in USDA Zone 5a – 7b. It survives winters down to planting zone 5a. Korean Arborvitae is native to Korea and the extreme northeast of China (Changbaishan).