Cardwellia

Cardwellia sublimis is a large tree reaching up to 40 m (130 ft) in height and a diameter of 2 m (6 ft 7 in), often becoming an emergent standing well above the canopy.[5][6] The bark is thin and there is usually no buttressing.[6][7] The leaves are alternate, dark green above with a silvery brown sheen below.[5][7][8] On seedlings the leaves are simple but on mature trees they are pinnately compound,[5] and there is a graduation of the leaf morphology as the tree grows (see gallery). Leaves on mature trees reach up to 65 cm (26 in) long with a petiole up to 11 cm (4.3 in) long[5] They have 3 to 10 pairs of oval to oblong leaflets, each of which is 9–18 cm (3.5–7.1 in) long and 4–7 cm (1.6–2.8 in) wide.[5][7][8]

The inflorescence is a raceme up to 16 cm (6.3 in) long,[5][8][9] with sessile flowers in pairs carried on a short peduncle.[7] They are produced above the tree canopy, and prolific − the canopy can be covered with the cream-white flowerheads in late spring and summer.[5][7]

The fruit are large, ellipsoidal, woody, dehiscent follicles about 8–11 cm (3.1–4.3 in) long and 5–6 cm (2.0–2.4 in) wide, carried on vertical peduncles and displayed above the canopy, creating a distinctive feature of this species.[5][7][8][10] They split along one side to release the seeds,[10] and will persist for some time both on the tree and on the ground after they have fallen.[7] They contain up to 14 winged seeds measuring about 7 by 3 cm (2.8 by 1.2 in).[5][7][8]

The Victorian colonial botanist Ferdinand von Mueller first described this species in 1865 based on material collected by John Dallachy in Rockingham Bay. It was published in his work Fragmenta Phytographiae Australiae[4][7][9]

Cardwellia sublimis is endemic to a small part of northeastern Queensland, occurring from the area around Rossville south to the Paluma Range National Park, and from the coastal flats to the adjacent ranges and tablelands. It grows in rainforest on a variety of soil types, and at altitudes from sea level to around 1,300 m (4,300 ft).[5][7][10][13]

Ants (Formicidae) are known to create wounds on the trunk of the northern silky oak by biting it, in order to access and consume the sugary sap.[16] The seeds are eaten by sulphur-crested cockatoos (Cacatua galerita) and native rats.[13]

The northern silky oak has been assessed as least concern by both the Queensland Department of Environment and Science and the International Union for Conservation of Nature (IUCN).[1][2] The IUCN states in its assessment summary that the "species was heavy logged in the past but this has stopped. Currently, the species has no immediate threats".[2]

Cardwellia sublimis was harvested extensively in the past for its highly-regarded timber,[2] which was widely used in houses of the traditional "Queenslander" style, especially for windows. It was also commonly used for furniture, joinery and flooring.[6][7] In limited supply today, it is now used mostly for cabinet work and veneers[5]

Attempts to grow Cardwellia sublimis in plantations have not been very successful,[7] however it has good potential as a park and street tree due to its large size, attractive foliage and showy flowering displays. It is readily propagated from seed (although seed must be fresh, stored for less than 6 weeks)[17] and has been grown successfully in Melbourne.[18]

• 
  Seedling, with simple leaves and cotyledons still attached
• 
  Sapling leaf, showing the intermediate pinnatisect morphology
• 
  Mature pinnate leaves
• 
  Underside of leaves

• 
  Inflorescences
• 
  Inflorescences
• 
  Mature fruit, some with seeds still enclosed
• 
  A dehisced fruit found on the ground

• Data related to Cardwellia sublimis at Wikispecies
• Media related to Cardwellia sublimis at Wikimedia Commons
• View a map of historical sightings of this species at the Australasian Virtual Herbarium
• View observations of this species on iNaturalist
• View images of this species on Flickriver