Stringybarks are common rough-barked forest and woodland trees occurring on a variety of sites and often on nutritionally poor soils.
In the classification of Brooker (2000), stringybarks belong to Eucalyptus subgenus Eucalyptus section Capillulus series Pachyphloius, being trees with coarsely fibrous "stringy" bark, shortly emergent oil glands adorned with obvious radiating hairs on stems and leaves of seedlings and juvenile growth (these oil glands appear stellate), axillary inflorescences with buds having only one operculum, flowers with reniform anthers, ovules in 2 rows, and ± pyramidal seeds with a distinctly terminal hilum. The adult leaves of all stringybark species have sparsely reticulate venation.
Stringybarks are often difficult to identify to species with certainty. In this edition of EUCLID we recognize 28 species in Australia, and they are restricted to South Australia, Victoria, New South Wales and Queensland. We tentatively divide the stringybarks into 5 groups as follows. The placement of species is suggestive of close relationships but frankly much work needs to be done to ascertain the validity of this.
1. Buds pedicellate, clavate - E. muelleriana, E. laevopinea.
2. Buds pedicellate, operculum beaked - E. macrorhyncha subsp. macrorhyncha and E. macrorhyncha subsp. cannonii.
3. Buds more or less sessile, angular longitudinally, operculum usually conical or sometimes rounded - E. mackintii, E. williamsiana, E. boliviana, E. youmanii, E. capitellata, E. camfieldii, E. bensonii.
4. Buds with tapering pedicels or sessile, fusiform to ovoid or obovoid, operculum conical or rounded, rarely slightly beaked, never strongly beaked - E. cameronii, E. globoidea, E. caliginosa, E. eugenioides, E. sparsifolia, E. tenella, E. mckieana, E. ligustrina, E. tindaliae, E. agglomerata.
5. Buds more or less sessile to shortly pedicellate, not angular, obovoid, operculum flat to obtuse or rarely acute - E. arenacea, E. baxteri, E. blaxlandii, E. imitans, E. serraensis, E. verrucata, E. victoriana.
One of the problems with identifying stringybarks is the occurrence of the "stringy" bark type in other species groups within the genus Eucalyptus. If the specimen you are trying to identify has the following features you definitely have a true stringybark:
1. bark rough and long-fibrous on trunk and main branches
2. leaves of crown have very little reticulate venation between the lateral veins (inspect fresh leaves with transmitted sunlight, using a 10X handlens)
3. juvenile leaves are scabrid or hairy at least for the lowermost pairs on coppice growth
4. buds have a single operculum (no circumferential scar on the bud surface caused by the shedding of the outer operculum as happens in many other eucalypts).
Other eastern Australian species and species groups that have superficially similar bark are: Eucalyptus obliqua, which has glabrous juvenile leaves; white mahogany species (8 species) which always have adult leaves with dense reticulation between the side veins, and glabrous juvenile leaves; peppermint species (E. radiata, E. dives, E. willisii) which are strongly scented and have glabrous juvenile leaves opposite and sessile for many pairs, but like stringybarks have sparsely reticulate venation in the adult leaves; and red mahogany species (E. resinifera, E. notabilis, E. pellita, E. scias) which have 2 opercula and shed the outer operculum during bud development, have densely reticulate venation in adult leaves and have glabrous juvenile leaves.
In the Northern Territory there is an endemic bloodwood species, Corymbia jacobsiana, which, singularly for the bloodwoods, has stringy bark. It differs otherwise from the true stringybarks in having a terminal branched inflorescence, buds with 2 opercula, oblong anthers, numerous ovules not arranged in discrete rows on the placenta, urceolate fruit, dorsiventrally flattened seed (saucer-shaped), adult leaves that are strikingly discolorous and juvenile leaves that have bristle-glands (setae).