Allthorn Plant Care

Allthorn (Koeberlinia spinosa) belongs to the Koeberliniaceae family within the Koeberlinia genus. Allthorn is native to the southwestern United States and northern Mexico known by several common names, including crown of thorns, allthorn, smokebush, and crucifixion thorn. Allthorn is also known as Junco.

Allthorn displays a sparse, upright shrub growth habit, reaching up to 6 ft tall with a spread of approximately 4 ft. Allthorn produces small greenish flowers in clusters.

Leaf size: approximately 2 inches.

Water a young or newly planted Allthorn every 14–21 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.

Allthorn thrives in full sun.

Koeberlinia spinosa tolerates temperatures of 50–90°F. Allthorn prefers humidity levels of 20–60%.

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

Feed Allthorn 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 and well-draining sandy soil with low fertility. Avoid low spots where water collects after rain.

Allthorn is suited to USDA Zone 12a.

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.

Allthorn can spread to about 4 ft (1.2 m) and reach about 6 ft (2 m) tall. Space plants about 4 ft (1.2 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 Allthorn 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.

Allthorn is frost-tender (hardy to USDA zone 12). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Allthorn can be propagated through seeds.

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

Allthorn is susceptible to spider mites, aphids. 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.

Allthorn grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Allthorn is native to the southwestern United States and northern Mexico known by several common names, including crown of thorns, allthorn, smokebush, and crucifixion thorn. In cooler regions, grow Allthorn as a houseplant or bring it indoors before the first frost.