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How to Grow Kalopanax – Castor Aralia, Tree Aralia 

Leaves of a castor aralia, Kalopanax septemlobus
Leaves of a castor aralia, Kalopanax septemlobus

Kalopanax–commonly called castor aralia or tree aralia–is a deciduous tree with a spreading, round habit. Kalopanax bears large palmately lobed leaves that can exceed one foot (30cm) in width. Kalopanax also bears large terminal, umbel-like tiny white flower panicles in late summer. Tiny black fruits follow the flowers and are quickly eaten by birds.

Kalopanax has a tropical look but is Hardy to USDA Zone 5. Kalopanax grows to 30 feet (10m) tall and wide. Kalopanax has a spiny trunk and spiny branches; it has relatively few branches. Spines eventually disappear from the trunk and larger branches.

Kalopanax is a genus of one species. It is native to forests in East Asia.

Leaves of a castor aralia, Kalopanax septemlobus
Leaves of a castor aralia, Kalopanax septemlobus

Get to Know Kalopanax 

  • Plant type: Deciduous tree 
  • Growing zones and range: Zones 5 to 9
  • Hardiness: Hardy to Zone 5
  • Height and width: To 30 feet (10m) tall and wide 
  • Growth rate: Fast 
  • Form and habit: Spreading, attractive, rounded habit 
  • Foliage: Large, in variably shaped, palmately lobed leaves, which are arranged alternately and vary from hairless to very hairy beneath 
  • Flowers: Large, terminal, umbel-like panicles of usually white, 4- or 5-petaled flowers 
  • Fruits: Spherical, tiny, blue-black fruit 
  • Bloom time: Late summer 
  • Uses: Specimen tree 
  • Common name: Castor aralia, Tree aralia 
  • Botanical name: Kalopanax 
  • Family name: Apaliaceae 
  • Origin: East Asia 

Where to Plant Kalopanax 

  • Plant Kalopanax in full sun or partial shade, preferably sheltered by other trees and shrubs. 
  • Plant Kalopanax in fertile, moist but well-drained soil. 

When to Plant Kalopanax 

  • Sow Kalopanax seed in containers in a cold frame in autumn.  

Planting and Spacing Kalopanax 

  • Plant Kalopanax 30 feet (10m) apart. 
  • Plant Kalopanax deep to accommodate the tree’s long root structure. 

How to Water and Feed Kalopanax 

  • Give Kalopanax regular water. 
  • Feed Kalopanax with an all-purpose organic fertilizer in spring. 
Spiky trunk of Kalopanax
The very spiky plant stem of the Kalopanax, also known as Castor Aralia.

How to Care for Kalopanax 

  • Prune young Kalopanax trees at any time during the spring; old trees rarely require pruning.  

Kalopanax Pests and Diseases 

  • Pests and diseases are infrequent.  

Kalopanax Propagation 

  • Take Kalopanax greenwood cuttings in early summer. 
  • Sow seeds in a container in a cold frame in autumn.

Kalopanax Varieties to Grow 

  • Kalopanax pictus, Castor aralia, spreading, deciduous tree with spines on the trunk and shoots, and variably shaped, shallowly to deeply 5- to 7-lobed, dark green leaves, to 14 inches (35cm) or more across, which vary from hairless to very hairy beneath. Large, umbel-like panicles, 8-12 inches (20-30cm) long, of small, 4- or 5-petaled white flowers, .06 inch (2mm) across, are borne in late summer, followed by spherical, blue-black fruit, .13 inch (3mm) across. To 30 feet (10m) tall and wide. China, Korea, Russia (South Kurile Islands, Sakhalin), Japan (Ryukyu Islands). 

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