Typical entire-leaved ailanthus (Ailanthus integrifolia subsp. integrifolia)

White Siris White Bean
Silhouette: T. Michael Keesey / License

Ailanthus integrifolia subsp. integrifolia: Botany and Habitat

Ailanthus integrifolia subsp. integrifolia is a majestic emergent tree that rises high above the dense rainforest canopies of Southeast Asia, New Guinea, and tropical Australia. Its Latin epithet integrifolia means "entire-leaved," referring to the smooth, untoothed margins of its large leaflets that set it apart from many temperate relatives.

First described in 1812 by Jean-Baptiste Lamarck, this autonymic subspecies represents the typical form of the species as classified by Dutch botanist Hans Peter Nooteboom in 1962, and it is an accepted taxon in the Plants of the World Online database.

Taxonomy

  • ∟ царство Plantae
  • ∟ division Tracheophytes (Vascular Plants)
  • ∟ subdivision Spermatophytes (Seed plants)
  • ∟ Angiosperms
  • ∟ mesangiosperms (Core angiosperms)
  • ∟ eudicots
  • ∟ core eudicots
  • ∟ Superrosids
  • ∟ rosids
  • ∟ malvids
  • ∟ order Sapindales
  • ∟ family Simaroubaceae (Quassia family)
  • ∟ genus Ailanthus (Tree of heaven)
  • ∟ species Ailanthus integrifolia (Entire-leaved tree of heaven)
  • ∟ subspecies Ailanthus integrifolia subsp. integrifolia (Typical entire-leaved ailanthus)

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Morphology

As a fast-growing rainforest giant, this tree can reach heights of 40 to 60 meters with a straight, cylindrical trunk covered in smooth, pale grey to brownish bark. Unlike some tropical trees, it typically forms a clean bole without prominent buttress roots.

Foliage and Crown

The crown is composed of large, odd-pinnate compound leaves (feather-like arrangements of leaflets along a central stalk) that grow from 30 to over 90 centimeters long. Each leaf bears several pairs of obliquely ovate to falcate (sickle-shaped) leaflets with completely smooth margins and asymmetric bases.

  • Glandular structures: Small, dark, flat glands are tucked on the lower surface near the base of the leaflets, secreting compounds that interact with local insects.
  • Surface texture: In this typical subspecies, both the leaf stalks and the glossy blades remain entirely hairless at maturity.

Flowers and Winged Fruits

The tree produces branched, axillary panicles (loose, multi-stemmed flower clusters) bearing small, five-petaled greenish-white flowers. It is predominantly dioecious, meaning male and female blossoms usually develop on separate trees, though hermaphroditic flowers also occur.

  • Corolla and calyx: In the typical subspecies, the outer petals are finely pubescent while the shallowly lobed cup-like calyx splits irregularly as the bud opens.
  • Samara dimensions: Following pollination, female flowers develop into cluster-borne samaras—flat, papery, single-seeded winged fruits that measure an impressive 11 to 22 centimeters in length.

Applications

In Southeast Asia and northern Australia, the pale, lightweight, and soft heartwood—commercially traded under the name white siris—is harvested for light indoor construction. Because the timber is easy to saw, plane, and peel without dulling tools, it is widely used in local woodworking industries.

  • Plywood and veneer: The straight, knot-free grain of the towering trunk makes it an ideal core material for rotary-cut veneer, laminated boards, and lightweight plywood.
  • Everyday goods: Craftspeople and factories process the low-density wood into matchboxes, matchsticks, wooden shoes, packing crates, and paper pulp.

Interesting facts

Growing as an emergent giant in humid equatorial forests presents a mechanical challenge: wind speeds drop dramatically beneath the dense upper canopy, making seed dispersal difficult for heavy-seeded trees. Ailanthus integrifolia subsp. integrifolia solves this through the aerodynamic architecture of its giant samaras, which are among the largest winged fruits in its genus.

Aerodynamic Precision

Each papery fruit functions as a self-stabilizing glider, engineered with a precisely balanced center of mass located directly over the central seed chamber. The vascular bundles (structural veins that transport water and nutrients during development) stiffen the leading edge and twist the papery blade slightly as it dries.

  • Autorotation mechanism: When released from a height of 50 meters, the slight longitudinal twist forces the samara into an immediate, stable spin that slows its descent.
  • Canopy clearance: This low terminal velocity allows even gentle thermal updrafts above the rainforest roof to carry the seed hundreds of meters away from the parent tree's shade.

Geography of distribution

  • India
  • Vietnam
  • Malaysia
  • Indonesia
  • Philippines
  • Papua New Guinea
  • Solomon Islands
  • Australia

Sources

Technical Information

Taxon Synonyms: Dysoxylum dasyphyllum, Ailanthus peekelii, Ailanthus guangxiensis

External Databases: GBIF, POWO

See also

True Araucarias

True Araucarias

Araucaria sect. Araucaria

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