Banksia
The
Banksia genus was first described and named by
Carolus Linnaeus the Younger in his April
1782 publication
Supplementum Plantarum systematis vegetabilium; hence the
full name for the genus is
"Banksia L.f." The genus name honours the
English botanist Sir
Joseph Banks, who collected the first
Banksia specimens in
1770, during
James Cook's first expedition.
Banksia belongs to the family
Proteaceae, subfamily
Grevilleoideae, and tribe
Banksieae.
Banksia and the closely related
Dryandra are placed together in subtribe
Banksiinae, mainly because in both genera the flowers occur in condensed heads. Recent research into the relationship between
Banksia and
Dryandra has suggested that
Dryandra should be sunk into
Banksia.
The exact number of species of
Banksia is a matter of some contention. The most recent authoritative synopsis, George (1999), listed 76 species. Since then a new species,
B. rosserae, has been published (Olde and Marriott, 2002), bringing the number of species to 77. However George (1999) gave subspecific rank to four taxa that had previously been promoted to species by Kevin Thiele and Pauline Ladiges in their 1996
cladistics analysis of the genus. Some Australian
herbaria have continued to follow Thiele and Ladiges (1996) in ranking these taxa as species, thus recognising 81 species. Furthermore Harden (2002) recognises the species
B. cunninghamii Sieber ex Reichb, even though both George (1999) and Thiele and Ladiges (1996) consider it a subspecies of
B. spinulosa. Finally,
B. paludosa subsp. astrolux is under review and is likely to be raised to species level soon.
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Distribution of Banksia within Australia |
All but one of the
Banksia species are
endemic to Australia. The exception is
B. dentata (Tropical Banksia), which occurs throughout northern Australia, and on islands to the north including
New Guinea and the
Aru Islands. The other species occur in two distinct geographical regions:
southwest Western Australia and eastern Australia. Southwest Western Australia is the main centre of
biodiversity; over three quarters of
Banksia species occur only there, from
Exmouth down to east of
Esperance. Eastern Australia has far fewer species, but these include some of best known and most widely distributed species, including
B. integrifolia and
B. spinulosa (Hairpin Banksia). Here they occur from the
Eyre Peninsula in South Australia right around the east coast up to
Cape York in
Queensland.
The vast majority of
Banksia are found in sandy (or gravelly) soils, though some populations of
B. marginata (Silver Banksia) and
B. spinulosa do occur on heavier, more clay-like, soils.
B. seminuda is exceptional for its preference for rich loams along watercourses. Most occur in
heathlands or low
woodlands, but
B. seminuda and
B. integrifolia both grow in
forests. Most species do not grow well near the
coast, and few species, including
B. rosserae and
B. elderiana (Swordfish Banksia), occur in
arid areas. Most of the eastern Australian species survive in
uplands, but of the Western Australian species only
B. solandri (Stirling Range Banksia) survives at high altitudes.
Studies of the south-western species have found the distribution of
Banksia species to be primarily constrained by rainfall. With the exception of
B. rosserae, no species tolerates annual rainfall of less than 200 millimetres, despite many species surviving in areas that receive less than 400 millimetres.
Banksia species are present throughout the region of suitable rainfall, with greatest speciation in cooler, wetter areas. Hotter, drier regions around the edges of the genus's range tend to have fewer species with larger distributions. The greatest species richness occurs in association with uplands, especially the Stirling Range.
s are heavy producers of
nectar, and so are important sources of food for nectariferous animals, including
honeyeaters and small mammals such as rodents, antechinus,
honey possums,
pygmy possums, gliders and
bats
. Many of these animals play a role in pollination of
Banksia. Varous studies have shown mammals and birds to be important pollinators
.An interesting observation by Carpenter in 1978 was that some banksias had a stronger odour at night possibly to attract mammal pollinators. Other associated fauna include the
larvae of
moths and
weevils, which burrow into the "cones" to eat the seeds and
pupate in the follicles; and
birds such as
cockatoos, who break off the "cones" to eat both the seeds and the
insect larvae.
A number of
Banksia species are considered rare or endangered. These include
B. brownii (Feather-leaved Banksia),
B. cuneata (Matchstick Banksia),
B. goodii (Good's Banksia),
B. oligantha (Wagin Banksia),
B. tricuspis (Pine Banksia), and
B. verticillata (Granite Banksia).
Response to fire
Banksia plants are naturally adapted to the presence of regular
bushfires in the Australian landscape. About half of
Banksia species are killed by bushfire, but these regenerate quickly from seed, as fire also stimulates the opening of sead-bearing follicles and the germination of seed in the ground. The remaining species usually survive bushfire, either because they have very thick bark that protects the trunk from fire, or because they have
lignotubers from which they can resprout after fire. In
Western Australia, the first group are known as 'seeders' while the second 'sprouters'.
Infrequent bushfires at expected intervals pose no threat, and are in fact beneficial for regeneration of banksia populations. However, too frequent bushfires can seriously reduce or even eliminate populations from certain areas, by killing seedlings and young plants before they reach fruiting age.
Many fires near urban areas are caused by arson, and thus the frequency is often much higher than fires would have been prior to human habitation. Furthermore, residents who live in areas near bushland may pressure local councils to burn areas near homes more frequently, to reduce fuel-load in the bush and thus reduce ferocity of future fires. Unfortunately there are often discrepancies in agreed frequency between these groups and conservation groups.
Dieback
Another threat to
Banksia is the
water mould Phytophthora cinnamomi, commonly known as "dieback". Dieback attacks the roots of plants, destroying the structure of the root tissues, "rotting" the root, and preventing the plant from absorbing water and nutrients.
Banksia's
proteoid roots, which help it to survive in low-nutrient soils, make it highly susceptible to this
disease. All Western Australian species are vulnerable, although most eastern species are fairly resistant.
Vulnerable plants typically die within a few years of infection. In
southwest Western Australia, where dieback infestation is widespread, infested areas of
Banksia forest typically have less than 30% of the cover of uninfested areas. Plant deaths in such large proportions can have a profound influence on the makeup of plant communities. For example, in southwestern Australia
Banksia often occurs as an understory to forests of
Jarrah (
Eucalyptus marginata), another species highly vulnerable to dieback. Infestation kills both the Jarrah overstory and the
Banksia understory, and over time these may be replaced by a more open woodland consisting of an overstory of the resistant Marri (
Corymbia calophylla), and an understory of the somewhat resistant Parrotbush (
Dryandra sessilis).
A number of species of
Banksia are threatened by dieback. Nearly every known wild population of
B. brownii shows some signs of dieback infection, which could possibly wipe it out within years.
. Other vulnerable species include
B. cuneata, and
B. verticillata.
Dieback is notoriously difficult to treat, although there has been some success with
phosphite and
phosphorous acid, which are currently used to inoculate wild
B. brownii populations. However this is not without potential problems as it alters the soil composition by adding
phosphorus. Some evidence suggests that phosphorous acid may inhibit proteoid root formation
.
Because dieback thrives in moist soil conditions, it can be a severe problem for
Banksias that are watered, such as in the cut flower industry and urban gardens.
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B. baxteri (Birds Nest Banksia), a species used in the cut flower trade, cultivated near Colac, Victoria |
In the garden
Banksias are popular garden plants in Australia because of their large, showy flower heads, and because the large amounts of
nectar they produce attracts
birds and small
mammals. Popular garden species include
B. spinulosa,
B. ericifolia,
B. aemula (Wallum Banksia ),
B. serrata (Saw Banksia),
Banksia media (Southern Plains Banksia) and the
cultivar Banksia 'Giant Candles'.
Banksia species are primarily propagated by seed in the home garden as cuttings can be difficult to strike. However commercial nurserymen extensively utilize the latter method (indeed, cultivars by nature must be vegetatively propagated by cuttings or grafting).
Over time, dwarf cultivars and prostrate species are becoming more popular as urban gardens grow ever smaller. These include miniature forms under 50cm high of
B. spinulosa and
B. media, as well as prostrate species such as
B. petiolaris and
B. blechnifolia .
Banksias possibly require more TLC (i.e. maintenance) than other Australian natives, though are fairly hardy if the right conditions are provided (sunny aspect and well drained sandy soil). They may need extra water during dry spells until established, which can take up to two years. If fertilised, only slow-release, low-
phosphorus fertilizer should be used, as the proteoid roots may be damaged by high
nutrient levels in the soil. All respond well to some form of pruning.
Within the Australian horticultural community there is an active subculture of
Banksia enthusiasts who seek out interesting flower variants, breed and propagate cultivars, exchange materials and undertake research into cultivation problems and challenges. The main forum for exchange of information within this group is
ASGAP's
Banksia Study Group.
Cut flower industry
With the exception of the
nursery industry,
Banksia have limited commercial use. Some species, principally
B. coccinea (Scarlet Banksia),
B. baxteri,
B. hookeriana (Hooker's Banksia),
B. sceptrum) (Sceptre Banksia),
B. speciosa (Showy Banksia) and
B. menziesii (Menzies' Banksia) are grown on
wildflower farms in Western and Southern Australia, as well as Israel and Hawaii, and the flower heads harvested for the
cut flower trade. Their nectar is also sought by
beekeepers, not for the quality of the
honey, which is often poor, but because the trees provide an abundant and reliable source of nectar at times when other sources provide little.
Woodworking
Banksia wood is a red colour with an attractive grain, but it is rarely used as it warps badly on drying. It is occasionally used for ornamental purposes, such as turnery and cabinet panelling, and has also been used to make
keels for small
boats. The large "cones" of
B. grandis are sliced up and sold as drink coasters; these are generally marketed as
souvenirs for international
tourists.
Indigenous uses
The
Indigenous people of south-western Australia would suck on the flower spikes to obtain the nectar, they also soaked the flower spikes in water to make a sweet drink
.
Banksia trees are a reliable source of grubs which are extracted as food.
Field guides and other technical resources
A number of field guides and other semi-technical books on the genus have been published. These include:
Field Guide to Banksias:Written by Ivan Holliday and Geoffrey Watton and first published in 1975, this book contained descriptions and colour photographs of species known at the time. It was largely outdated by the publication of Alex George's classic 1981 monograph, but a revised and updated second edition was released in 1990.
;The Banksias:This three volume monograph contains
watercolour paintings of every
Banksia species by renowned
botanical illustrator Celia Rosser, with accompanying text by Alex George. Its publication represents the first time that such a large genus has been entirely painted. Published by Academic Press in association with
Monash University, the three volumes were published in 1981, 1988 and 2000 respectively.
;The
Banksia Book:Begun by Fred Humphries and Charles Gardner, both of whom passed away before its completion,
The Banksia Book was eventually completed by Alex George and first published in 1984. A comprehensive volume containing colour illustrations of every species, it is now in its third edition, published in 1996. This book is sought after by many and becoming hard to find.
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The Banksia Atlas:In 1983 the
Australian Biological Resources Study (ABRS) decided to pilot an Australia-wide distribution study of a significant plant genus.
Banksia was chosen because it was a high-profile, widely distributed genus that was easily identified, but for which distribution and habitat was poorly known. The study mobilised over 400 volunteers, collecting over 25,000 field observations over a two year period. Outcomes included the discovery of two new species, as well as new varieties and some rare colour variants, and discoveries of previously unknown populations of rare and threatened species. The collated data was used to create
The Banksia Atlas, which was first published in 1988.
.
;Banksias, Waratahs and Grevilleas and all other plants in the Australian Proteaceae family:Written by J. W. Wrigley and M. Fagg, this was published by Collins Publishers in 1989. A comprehensive text on all the Proteaceae genera with good historical notes and an overview of the 1975 Johnson & Briggs classification. It is out of print and hard to find.
May Gibb's "Banksia men"
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B. aemula seed pod, ANBG, Canberra, a possible inspiration for Gibbs |
Perhaps the best known cultural reference to
Banksia is the "big bad Banksia men" of
May Gibbs' children's book
Snugglepot and Cuddlepie. Gibb's "Banksia men" are modelled on the appearance of aged
Banksia "cones", with follicles for eyes and other facial features. There is some contention over which species actually provided the inspiration for the "Banksia men": the drawings most resemble the old cones of
B. aemula, but
B. attenuata (Slender Banksia) has also been cited, as this was the species that Gibbs saw as a child in Western Australia.
Other cultural references
In 1989, the
Banksia Environmental Foundation was created to support and recognise people and organizations that make a positive contribution to the environment. The Foundation launched the annual
Banksia Environmental Awards in the same year.
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The Banksia Page of
ASGAP*
Banksia Study Group of
ASGAP*
Banksia Online Discussion Group
