Banksia - Background

Introduction

Banksia is a genus of over 200 species in the Protea family (Proteaceae). All species occur in Australia with one (B.dentata) extending to islands to Australia's north. Banksias can be found in most environments; the tropics, sub-alpine areas, the coast and desert areas. The most diversity in the genus occurs in the south of Western Australia where most of the species occur.

Until recently, the genus comprised 78 species, most with the familiar candle-like shaped flower clusters. However, a paper published in February 2007 (see below) proposed that the genus Dryandra be subsumed into Banksia. The paper published new names in Banksia for all (then) currently recognised Dryandra species. This revised classification has been accepted by the Council of Heads of Australasian Herbaria and the new names now appear on Florabase (the website for the Western Australian Herbarium) and in the Australian Plant Census, which is the main online reference for names of Australian native plants.

Mast A R and Thiele K; The transfer of Dryandra R.Br. to Banksia L.f. (Proteaceae); Australian Systematic Botany, 26 February 2007

This reclassification increased the number of Banksia species significantly but the revised classification has not met with universal approval. For example, Alex George, a highly respected authority on both Banksia and Dryandra, strongly opposes the change on scientific grounds. The two opposing views are set out in the following articles:

As ANPSA recognises the Australian Plant Census as the authority on plant names, the revised classification has now been adopted on the ANPSA website. However, recognising that the reclassification is controversial, the former Dryandra names are listed alongside the corresponding Banksia names, where appropriate. Regardless of this scientific re-classification, species previously classified under Dryandra remain quite distinctive horticulturally and will undoubtedly still be called dryandras in common usage.

Characteristics of Banksia

   Banksia flower opening
   Stages of opening of a Banksia flower.
Photo: Brian Walters

Banksia flowers are quite small but they occur in dense clusters which, in some species, can number several thousand individuals. The sequence of opening of each flower goes through several stages:

  1. In bud, each flower appears as an elongated narrow tube (the perianth) comprising four segments each having an anther containing pollen at its tip.
  2. As the flower opens, the perianth segments separate to reveal a narrow style. Just before the flower fully opens the anthers transfer their pollen to the tip of the style (the stigma)
  3. Finally, the style separates from the perianth. At this stage the style and stigma, with attached pollen, is called a 'pollen presenter' (i.e. it is 'presenting' the pollen to a pollinator, usually a bird or small marsupial, which acts as the agent to transfer pollen from one flower to another for fertilisation.

This sequence is shown in the accompanying diagram and is fairly typical of most members of the Proteaceae.

In general terms the genus Banksia can be broadly characterised into three groups, based on the arrangement of the flower clusters:

  • Flowers arranged around a vertical axis, giving the familiar cylindrical inflorescence (previously classified as Banksia subgenus Banksia).
  • Flowers are arranged in cone-shaped clusters without bracts (previously classified as Banksia subgenus Isostylis).
  • Flowers are arranged in cone-shaped clusters surrounded by overlapping, scale-like bracts which often form a conspicuous part of the inflorescence (previously classified as genus Dryandra).

This grouping is illustrated below.

Banksia menziesii    Banksia cuneata    Dryandra quercifolia
Family Relationships
Left: Banksia menziesii, a 'typical' Banksia with flowers arranged around a vertical axis.
Centre: Banksia cuneata, with cone-shaped flower clusters.
Right: Banksia heliantha (syn. Dryandra quercifolia), with cone-shaped flower clusters surrounded by bracts.
Photos: Jim Barrow, Brian Walters

The flower clusters of most Banksia species are cream, yellow, brown or orange in colour. There are a few species where the inflorescence can have a pink colour in certain forms (eg. B.praemorsa, B.fraseri, B.undata).

   Banksia oblongifolia seed cones
   Opened seed follicles
after a fire

Photo: Brian Walters

The flowers are followed by more or less woody follicles each containing one or two seeds. In 'typical' banksias, the seeds occur in woody seed "cones" in which the seeds are contained within closed follicles, two seeds per follicle. In the former genus Dryandra, the follicles are hidden within the spent flower clusters. In both cases, these follicles usually remain tightly closed unless stimulated to open by heat, such as following a bushfire but, with a few species, the seed is released annually. The seeds themselves have papery wings which allows them to be distributed by wind.

Most banksias are small to medium shrubs but there are many which are prostrate with underground stems and a few can become large trees. Those species native to areas where fires occur at regular intervals often have a "lignotuber", a woody swelling at or below ground level from which regeneration of the plant can occur if the above ground stems are destroyed. Other species are killed in fire, with seedlings sprouting in their place.

Discovery

Archaeological evidence suggests that banksias or Banksia-like plants have existed for over 40 million years. The first humans to discover and make use of Banksia plants were the Australian aborigines who used the nectar from the flowers as part of their diet.

The first Europeans to observe banksias were probably Dutch explorers who made several landfalls along the West Australian coast during the 17th and early 18th centuries. No botanical collections were made, however, until the discovery of the east coast of Australia by Captain James Cook in the Endeavour in April 1770. Accompanying Cook were botanists Joseph Banks and Daniel Solander who collected many new species at Botany Bay including four which would later be included in a new genus, Banksia, named in honour of Joseph Banks' contribution to botany. The four species collected were B.serrata, B.ericifolia, B.integrifolia and B.robur. Later, on the same voyage, Banks and Solander collected a fifth species (B.dentata) on the north Queensland coast.

New banksias are still being discovered from time to time. Recent discoveries include:

  • Banksia rosserae - Near Mt Magnet, Western Australia (2002)
  • Banksia croajingolensis - East Gippsland, Victoria (2007)

◄◄ Banksia Index    Top ▲