Gardenia actinocarpa

This species grows as an evergreen understory plant, reaching up to 5 m (16 ft) in height but flowering and fruiting once it reaches around 1 m (3 ft 3 in). It is a spindly arborescent shrub with a stem diameter of around 3 cm (1.2 in) at breast height.[3][4][5]

The leaves are opposite and chartaceous (papery) with wavy edges, glossy mid green above and paler below, and attached to the twigs with a petiole around 9 mm (0.35 in) long. They measure between 10–27 cm (3.9–10.6 in) long and 4–7 cm (1.6–2.8 in) wide, and are generally obovate in shape. They have a long attenuate (tapering) base and an extended "drip tip". Stipules are conical, up to 7 mm (0.28 in) long and resinous.[3][4][5]

Flowers are terminal, solitary, actinomorphic and 6-merous, borne on pedicels between 5 and 15 mm (0.20 and 0.59 in) long. The calyx tube is green, coriaceous, and has six external longitudinal ridges extending into the laterally compressed calyx lobes. The corolla is about 50 mm (2.0 in) in diameter, white with six elliptical petals, and a corolla tube measuring about 15–25 mm (0.59–0.98 in) long.[3][4][5]

Fruits are green, ellipsoidal, up to 46 mm (1.8 in) long by 32 mm (1.3 in) wide, glabrous, with six longitudinal ridges, and the calyx lobes remain attached at the apex. They contain a number of seeds which are up to 4.5 mm (0.18 in) diameter by 1.6 mm (0.063 in) thick.[3][4][5]

Gardenia actinocarpa was described by the Australian botanist C.F. Puttock from samples collected by Geoff Tracey and Leonard Webb in 1973 from Oliver Creek, near Cape Tribulation, Queensland. Puttock's paper was published in Austrobaileya, the annual journal of the Queensland Herbarium, in 1988.[2][3][4][7]

This rare species is found in a very restricted range, consisting of rainforested alluvial lowlands in a single watershed of the Daintree rainforest. A study published in 2001 has suggested that this is a relatively new species which is still expanding its range.[6]

G. actinocarpa is classified as endangered under the Australian Government's Environment Protection and Biodiversity Conservation Act 1999 and the Nature Conservation Act 1992 of Queensland.[1][8] Threats facing the species include the potential fragmentation of its habitat, limited female fecundity (when compared with related species), rapid loss of seed viability, and geographical barriers.[6]

As of 7 April 2022, it has not been assessed by IUCN.

• 
  Male flower
• 
  Cairns Botanic Gardens, May 2021
• 
  Developing fruit. Cairns Botanic Gardens April 2022
• 
  Calyx, shortly after corolla has detached

• Data related to Gardenia actinocarpa at Wikispecies
• Media related to Gardenia actinocarpa at Wikimedia Commons
• See a map of recorded sightings of Gardenia actinocarpa at the Australasian Virtual Herbarium
• See a map of recorded sightings of Gardenia actinocarpa on iNaturalist.