Black Walnut Plant Care

Black Walnut (Daphnandra melasmena) belongs to the Atherospermataceae family within the Daphnandra genus.

Black Walnut displays a tall, upright tree growth habit, reaching up to 30 ft tall with a spread of approximately 15 ft. Black Walnut produces small, inconspicuous flowers.

Leaf size: approximately 6 inches.

Water a young or newly planted Black Walnut 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.

Black Walnut thrives in partial to full shade. The optimal light range is 100–500 lux. Avoid placing Black Walnut in direct, harsh sunlight for extended periods, as this can scorch the foliage.

Daphnandra melasmena tolerates temperatures of 60–80°F. Black Walnut prefers humidity levels of 50–70%. A pebble tray or humidifier helps maintain adequate moisture around the plant.

Rich, well-draining soil with high organic content. Good drainage is essential for Black Walnut to prevent waterlogging, which leads to root rot and fungal issues.

Feed Black Walnut 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 partial to full shade and rich, well-draining soil with high organic content. Avoid low spots where water collects after rain.

Black Walnut 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.

Black Walnut can spread to about 15 ft (4.6 m) and reach about 30 ft (9 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 Black Walnut 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.

Black Walnut 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.

Black Walnut can be propagated through seeds, cuttings. Similar propagation techniques also apply to daphnandra apatela plant care, which shares the same genus.

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Black Walnut is susceptible to aphids, 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.

Black Walnut grows outdoors in USDA Zone 13a. It survives winters down to planting zone 13a. In cooler regions, grow Black Walnut as a houseplant or bring it indoors before the first frost.