Using Bark Characteristics in the Identification of Australian Tree Species

Bark texture ranges from the very smooth (polished-like) to the sharp roughness of tessellated (scaly) or fissured surfaces. A finely rough texture is referred to as granular. The term fissured relates to finer cracks, whereas being furrowed depicts wider grooves. The description stringy is used for bark that has a fibrous (rough rope-like) quality and can be pulled apart into strings. The aptly named Stringybarks (Eucalyptus spp.) are good examples. The quality of being flaky and papery is a common feature for the Paperbarks (Melaleuca spp.). Bark texture often changes with age and can be considerably different on the trunk when compared to branches. Bark texture is perceived visually and by touch. From soft to very hard, consistency is perceived when bark is pressed. Terms like corky, spongy, softly fibrous, firm and very hard express degrees of consistency. These bark qualities are reflected in tree names such as Soft Corkwood (Ackama paniculata) or Ironbarks (Eucalyptus spp.), on the opposite side of the scale. Consistency can depend on moisture levels present in the bark, e. g. hard and brittle when dry, spongy and crumbly when wet.

A specific scent, emitted when bark is rubbed, can enable the positive identification of some tree species. This is reflected in the common naming of trees such as; the Celerywood (Polyscias elegans) (1), Onion Cedar (Owenia cepiodora) (2), Sassafras (3), the Peppermints (a group of Eucalyptus spp.) (4) and a range of other species.

With exceptions, most rainforest trees feature a thin bark that is constantly shed in small particles and doesn’t protect the vital cambium from heat exposure (1). Consequently rainforest trees are killed by a high intensity bushfire. In contrast tree species, which inhabit flammable environments, such as Eucalypts, Paperbarks (Melaleuca spp.), Bottlebrushes (Callistemon spp.) and Tea Trees (Leptospermum spp.) (2) produce a thick bark that offers protection from fires. The bark thickness of these trees increases with age, as most of the old dead bark is retained. The thickness of bark is often hard to judge, but fissures and furrows can give some indication.

Trees producing bark of different types are a common occurrence in the transition zones (ecotones) between rainforests and drier open forests. In these and other environments, which are infrequently exposed to lower intensity fires, a stocking of thick rough bark on the lower part of the trunk is sufficient in protecting the tree from damage. The upper half of the trunk, limbs and branches are covered in a contrasting thinner and smooth bark, which is not retained and often sheds in strips or plates. The Brush Box (Lophostemon confertus) (3) and a number of Eucalyptus [Corymbia] species; Flooded Gum (E. grandis), Cadaghi (C. torelliana) (4), Carbeen (C. tessellaris) and the Shining Gum (Eucalyptus nitens) are good examples.