Harmsiopanax Warb.

Timothy M. A. Utteridge and Laura V. S. Jennings (2022). Trees of New Guinea. Kew Publishing. Royal Botanic Gardens, Kew

Distribution

A genus of three species, with one species found throughout Java, Sulawesi, and the Lesser Sunda Islands, and the other two species in New Guinea: Harmsiopanax ingens Philipson and H. harmsii K.Schum.

Morphology General Habit

Sparingly branched or single-trunked trees to 18 m; monocarpic (in New Guinea); trunk, petioles, and leaves spiny. Leaves large (to 1 m in diameter), simple, palmately lobed and sometimes peltate, margins dentate or crenate, borne in terminal clusters, often woolly hairy especially on the underside

Morphology Reproductive morphology Inflorescences

Inflorescences terminal, branched panicles, developing after the leaves have fallen, often large (up to 5 m long and 5 m wide), umbellules arranged racemosely on the ultimate branchlets

Morphology Reproductive morphology Flowers

Flowers bisexual (in New Guinea), 5-merous, pedicels not articulated below the ovary; calyx a minute rim; petals 5, free, valvate, not clawed at the base; stamens 5, dorsifixed; disk conical, deeply cleft between the 2 styles; ovary inferior, narrowly obconic, densely bristly, 2-celled; styles 2, subulate

Morphology Reproductive morphology Fruits

Fruit dry, splitting into 2 mericarps, each 3-ribbed and bearing the persistent style.

Ecology

Members of the genus can usually be found in more open habitats such as regrowth, grassy hillsides and roadsides, and can form considerable stands together with other ‘secondary’ or seral taxa, but can also be found in forested areas, from lowland to montane forests from 100–3600 m.

Recognition

Harmsiopanax can be recognised by the monocarpic habit, being spiny throughout with prickles even on the leaves (usually on the midrib and venation), the simple, palmately lobed leaves up to 1 m in diameter (often pale hairy below due to branched hairs at the base of the bristles), and the massive terminal inflorescences developing after the leaves have fallen with numerous flowers developing into dry fruits. Each plant, however, may be a monocarpic ‘ramet’ from a more extensive subsurface clone.