Sour Hardwood

It is a large rainforest tree reaching up to 35 m (115 ft) in height, with brown furrowed bark and (sometimes) buttresses. The leaves are simple, arranged alternately or in whorls on the twigs, and are obovate in shape. They can grow up to 21 cm (8 in) long and are attached to the twig by a petiole (leaf stem) up to 12 mm (0.5 in) long. The inflorescences are produced from the leaf axils and are about 10 cm (4 in) long. They carry numerous quite small flowers, each with five white petals about 3 mm (0.12 in) long. Stamens number about 100 and are arranged in groups opposite the petals, each group with up to four sterile stamens and 15–20 fertile ones. The woody fruit is about 18 mm (0.7 in) diameter, with three locules or segments, and they usually contain one or two seeds per fruit.

It occurs in two main populations to the north and south of Cairns, one near Cape Tribulation and another broader population from about Fishery Falls to Mourilyan. It grows in lowland rainforest at altitudes up to 100 m (330 ft), often close to swamps.

The name Ristantia is an anagram of Tristania.The species epithet is derived from the Ancient Greek words păkhŭ́s, thick, and spérma, seed, as a reference to the hard woody capsules.