Baeckea gunniana

Baeckea gunniana is a smooth, compact shrub growing to 1.5 m high, although can reach up to 2 m at lower altitudes.[3] It is sometimes prostrate or spreading over rocks and boulders.[4] Branchlets are brown with a flat segment on a papery or fibrous brown bark.[2] Leaves are small (2–4 mm long; 0.6-0.8 mm wide) and crowded, obovate to oblong shaped with a blunt apex,[3] and with entire margins and petioles c. 0.5 mm long.[2] The flowers are white, small and numerous, borne solitarily in the upper leaf axils.[5] Sepals are triangular and obtuse, with a corolla 4–5 mm in diameter and circular petals c. 1–1.8 mm long. Stamens 4–6, not opposite petals. The ovary has a single locule. Style is terete and only slightly inserted into the ovary summit.[3] The unilocular ovary, where the pendulous placenta and ovules are enclosed by a single membrane, is characteristic to the species and unique in the genus.[2]

The fruit is green and cup-like when immature[5] and woody, dehiscent capsule at maturity.[3] Seeds are small and angular, remaining inconspicuous on the ground upon release.[3][5] Seed coat/covering or testa of some Baeckea species has been recorded to form a physical barrier inhibiting seed germination.[3] This may be reverted by removing or nicking the testa using a needle or scalpel, improving the rate of germination.[3] B. gunniana can also be vegetatively propagated from cuttings of semi-hardened new growth.

Distribution is restricted to alpine or subalpine regions, from Mt Ginini in ACT to south-west Tasmania.[3][2] Baeckea gunniana is most prevalent at high altitudes between 1000 to 1400 m. However, it has been observed to grow above 2000 m near Mt Kosciusko, and as low as 450 m in western Tasmania.[2] All species in the genus Baeckea are confined to Australia, except for the type species, B. frutescens (L.), which extends from eastern Australia through Malesia to China.[2]

Baeckea gunniana is commonly found growing with species such as Callistemon pityoides, Epacris paludosa, and Empodisma minus, in heathlands or boggy sedgeland.[2] It is also common near creeks, and sometimes in shaded areas under Eucalyptus spp.[3]

The species was first formally described by the German botanist Johannes Conrad Schauer in 1843.[6]

The closest Myrtaceae sensu stricto lineage is represented by two fleshy fruited (Myrcianthes and Acmena) and three dry fruited taxa. Angophora and Backhousia are sister genera to Baeckea, belonging to a dry-fruited lineage of Myrtaceae.[7]

Baeckea leaves are edible and often used as a tea substitute because of their aromatic citrus-like flavour.[1][8] Extracts from B. gunniana have been found to inhibit the activity of DNA Polymerase enzyme.[9] It forms an integral part of the Broad-toothed mouse habitat in NSW, Australia, providing protection from predators and other large grazers.[8]

White Myrtaceae flowers of Baeckea gunniana Photo © Greg Jordan. © 2019 University of Tasmania