Eucalyptus crebra, commonly known as the narrow-leaved ironbark, narrow-leaved red ironbark or simply ironbark, and as muggago in the indigenous Dharawal language, is a species of small to medium-sized tree endemic to eastern Australia. It has hard, rough "ironbark" from its trunk to small branches, linear to lance-shaped adult leaves, flower buds in groups of seven, nine or eleven, white flowers and cup-shaped, barrel-shaped or hemispherical fruit. A variable species, it grows in woodland and forest from the Cape York Peninsula to near Sydney. It is an important source of nectar in the honey industry and its hard, strong timber is used in construction. Description Eucalyptus crebra is a tree that typically grows to a height of and forms a lignotuber. It has persistent thick, rough, deeply furrowed, greyish black "ironbark" from the base of its trunk to the small branches. Young plants and coppice regrowth have linear to lance-shaped or curved leaves long and wide. Adult leaves are linear to lance-shaped, the same dull green to greyish colour on both sides, long and wide on a petiole long. The flower buds are arranged in groups of seven, nine or eleven, usually on a branching inflorescence on the ends of branchlets. Each group is carried on a peduncle long, the individual buds on a pedicel long. Mature buds are club-shaped, spindle-shaped, or diamond-shaped to oval, long and wide and green to yellow with a conical to rounded operculum. Flowering has been recorded in most months and the flowers are white. The fruit is a woody cup-shaped, barrel-shaped or hemispherical capsule long and wide on a pedicel long. Taxonomy and naming Eucalyptus crebra was first formally described in Journal and Proceedings of the Linnean Society, Botany by Victorian state botanist Ferdinand von Mueller in 1859. The specific epithet is the Latin adjective crebra meaning "thick", "close" or "numerous", referring to the species' abundance. Narrow-leaved ironbark has included several species, including E. drepanophylla and E. xanthoclada but these are regarded as synonyms by the Australian Plant Census. Eucalyptus repanophylla is accepted as a separate species by the Queensland Government. Other similar species include E. exilipes, E. granitica, E. staigeriana, E. quadricostata and E. whitei. Distribution and habitat The narrow-leaved ironbark grows in sandy soils in woodland and forest from Picton, southwest of Sydney, north through New South Wales and Queensland to the vicinity of Cairns. Uses The tree has a hard, strong,