Geijera is a small genus of shrubs and trees in the citrus family Rutaceae, order Sapindales, with around five accepted species distributed across New Guinea, Australia, and New Caledonia. The genus was first formally described in 1834 by the Austrian botanist Heinrich Wilhelm Schott in his work Rutaceae – Fragmenta Botanica, with Geijera salicifolia designated as the type species.
Members of the genus are characterised by simple, alternate leaves and small bisexual flowers borne in many-flowered panicles in the upper leaf axils and at the ends of branchlets. The flowers typically have five — occasionally four — sepals fused at the base, white or cream-coloured petals up to 2 mm long, and stamens arranged opposite the sepals. The fruit consists of up to five more or less spherical follicles joined at the base, each containing a single shiny black seed.
Most species favour tropical or subtropical rainforest habitats. Three species are native to New Caledonia, and three occur in Australia, two of which are endemic to the continent. The most widespread Australian representative is Geijera parviflora, commonly known as wilga, a drought-tolerant tree of the inland plains valued as fodder for livestock. Geijera salicifolia, the Queensland brush box or scrub wilga, ranges from New Guinea and New Caledonia through coastal Queensland and New South Wales to the Northern Territory.
Etymology
The genus name Geijera honours J.D. Geijer, a 17th-century Swedish botanist. The name was established by Schott in 1834 when he formally described the genus in his botanical monograph on the Rutaceae.
Distribution
Geijera species are native to New Guinea, Australia, and New Caledonia. Most species grow in tropical or subtropical rainforest. Three species occur in New Caledonia and three in Australia, two of which are endemic; Geijera parviflora extends into drier inland habitats across eastern and southern Australia.
Taxonomy Notes
The genus was formally described in 1834 by Schott (Rutaceae – Fragmenta Botanica), with Geijera salicifolia as the type species. GBIF recognises five accepted species. Geijera helmsiae and G. paniculata — included by Plants of the World Online — are treated as synonyms of Coatesia paniculata by the Australian Plant Census.
