Kaua'i prickly ash Plant Care

Kaua'i prickly ash (Zanthoxylum kauaense) belongs to the Rutaceae family within the Zanthoxylum genus. Kaua'i prickly ash is native to dry and wet forests. Kaua'i prickly ash is also known as A'e.

Kaua'i prickly ash displays an upright, small tree growth habit, reaching up to 10 ft tall with a spread of approximately 6 ft. Kaua'i prickly ash produces small clusters of white or greenish flowers.

Leaf size: approximately 4 inches.

Water a young or newly planted Kaua'i prickly ash 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.

Kaua'i prickly ash thrives in full sun to partial shade.

Zanthoxylum kauaense tolerates temperatures of 60–85°F. Kaua'i prickly ash prefers humidity levels of 40–70%.

Well-draining loamy soil with added sand and perlite for improved drainage. Good drainage is essential for Kaua'i prickly ash to prevent waterlogging, which leads to root rot and fungal issues.

Feed Kaua'i prickly ash every 6 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 partial shade and well-draining loamy soil with added sand and perlite for improved drainage. Avoid low spots where water collects after rain.

Kaua'i prickly ash is suited to USDA Zone 13a.

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.

Kaua'i prickly ash can spread to about 6 ft (1.8 m) and reach about 10 ft (3 m) tall. Space plants about 6 ft (1.8 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 Kaua'i prickly ash 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.

Kaua'i prickly ash is frost-tender (hardy to USDA zone 13). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Kaua'i prickly ash can be propagated through seeds, stem cuttings. Similar propagation techniques also apply to sichuan pepper plant care, which shares the same genus.

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

Kaua'i prickly ash is susceptible to aphids, scale insects, citrus leaf miners. 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.

Kaua'i prickly ash grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. Kaua'i prickly ash is native to dry and wet forests. In cooler regions, grow Kaua'i prickly ash as a houseplant or bring it indoors before the first frost.