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Banksia


Banksia prionotes


Plant Characteristics
Habit   shrub

Lifespan: ⌛ perennial
Origin: ✈ Australia
Cultivation
Exposure: ☼ sun
Water: ◍ moderate, dry
Scientific Names

Proteaceae >

Banksia >


Banksia is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. When it comes to size, banksias range from prostrate woody shrubs to trees up to 30 metres tall. They are generally found in a wide variety of landscapes; sclerophyll forest, (occasionally) rainforest, shrubland, and some more arid landscapes, though not in Australia's deserts. They are of economic importance to Australia's nursery and cut flower industries.

Banksias grow as trees or woody shrubs. Trees of the largest species, B. integrifolia (Coast Banksia) and B. seminuda (River Banksia), often grow over 15 metres tall, some even grow to standing 30 metres tall.[1] Banksia species that grow as shrubs are usually erect, but there are several species that are prostrate, with branches that grow on or below the soil.

The leaves of Banksia vary greatly between species. Sizes vary from the narrow, 1–1½ centimetre long leaves of B. ericifolia (Heath-leaved Banksia), to the very large leaves of B. grandis (Bull Banksia), which may be up to 45 centimetres long. The leaves of most species have serrated edges, but a few, such as B. integrifolia, do not. Leaves are usually arranged along the branches in irregular spirals, but in some species they are crowded together in whorls. Many species have differing juvenile and adult leaves (e.g. Banksia integrifolia has large serrated juvenile leaves).

The character most commonly associated with Banksia is the flower spike, an elongated inflorescence consisting of a woody axis covered in tightly-packed pairs of flowers attached at right angles. A single flower spike generally contains hundreds or even thousands of flowers; the most recorded is around 6000 on inflorescences of B. grandis. Not all Banksia have an elongate flower spike, however: the members of the small Isostylis complex have long been recognised as Banksias in which the flower spike has been reduced to a head; and recently the large genus Dryandra has been found to have arisen from within the ranks of Banksia, and sunk into it as B. ser. Dryandra. Thus fewer than half of the currently accepted Banksia taxa possess the elongated flower spike long considered characteristic of the genus.

B. marginata flower spike before and after anthesis

Banksia flowers are usually a shade of yellow, but orange, red, pink and even violet flowers also occur. The colour of the flowers is determined by the colour of the perianth parts and often the style. The style is much longer than the perianth, and is initially trapped by the upper perianth parts. These are gradually released over a period of days, either from top to bottom or from bottom to top. When the styles and perianth parts are different colours, the visual effect is of a colour change sweeping along the spike. This can be most spectacular in B. prionotes (Acorn Banksia) and related species, as the white inflorescence in bud becomes a brilliant orange. In most cases, the individual flowers are tall, thin saccate (sack-shaped) in shape.

Seed separator of a Silver Banksia (Banksia marginata) with winged seeds still cohering

Occasionally, multiple flower spikes can form. This is most often seen in Banksia marginata and B. ericifolia[2][3] (pictured right).

Infructescence of B. integrifolia, with non-persistent flowers; and B. marginata, with persistent flowers

As the flower spikes or heads age, the flower parts dry up and may turn shades of orange, tan or dark brown colour, before fading to grey over a period of years. In some species, old flower parts are lost, revealing the axis; in others, the old flower parts may persist for many years, giving the fruiting structure a hairy appearance. Old flower spikes are commonly referred to as "cones", although they are not: cones only occur in conifers and cycads.

Despite the large number of flowers per inflorescence, only a few of them ever develop fruit, and in some species a flower spike will set no fruit at all. The fruit of Banksia is a woody follicle embedded in the axis of the inflorescence. These consist of two horizontal valves that tightly enclose the seeds. The follicle opens to release the seed by splitting along the suture, and in some species each valve splits too. In some species the follicles open as soon as the seed is mature, but in most species most follicles open only after stimulated to do so by bushfire. Each follicle usually contains one or two small seeds, each with a wedge-shaped papery wing that causes it to spin as it falls to the ground.

Banksia prionotes seedlings after fire, Burma Road Nature Reserve, WA

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 seed-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, banksias of the first group are known as 'seeders' and the second group as 'sprouters'.

Banksia attenuata resprouting after fire, Burma Road Nature Reserve, WA

Most of species are shrubs, only few of them can be found as trees and they are very popular because of their size, the tallest species are: B. integrifolia having its subspecies B. integrifolia subsp. monticola notable for reaching the biggest banksias and it is the most frost tolerant in this genus, B. seminuda, B. littoralis, B. serrata; species that can grow as small trees or big shrubs: B. grandis, B. prionotes, B. marginata, B. coccinea, B. speciosa and B. menziesii. Due to their size these species are popularly planted in parks, gardens and streets, the remaining species in this genus are only shrubs.

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 50 cm 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.

Cultivation

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Propagation

Heat cone in hot oven (to emulate a fire) and then extract seed to plant.

Pests and diseases

A 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.

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.[4]

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.

Species

This is an alphabetically ordered list of Banksia species, as of 2007. This list includes all species recognised as current by the Australian Plant Name Index, and also contains all species transferred to Banksia from Dryandra by Austin Mast and Kevin Thiele in 2007.

  1. B. acanthopoda
  2. B. aculeata - Prickly Banksia
  3. B. acuminata
  4. B. aemula - Wallum Banksia
  5. B. alliacea
  6. B. anatona
  7. B. aquilonia - Northern Coastal Banksia, Jingana (Jirrbal, Girramay)
  8. B. arborea
  9. B. archaeocarpa (fossil)
  10. B. arctotidis
  11. B. armata
  12. B. ashbyi - Ashby's Banksia, Orange Banksia
  13. B. attenuata - Slender Banksia, Candlestick Banksia, Coast Banksia
  14. B. audax
  15. B. aurantia
  16. B. baueri - Woolly Banksia, Woolly-spiked Banksia, Possum Banksia
  17. B. baxteri - Baxter's Banksia, Bird's Nest Banksia
  18. B. bella
  19. B. benthamiana - Bentham's Banksia
  20. B. bipinnatifida
  21. B. biterax
  22. B. blechnifolia
  23. B. borealis
  24. B. brownii - Brown's Banksia, Feather-leaved Banksia
  25. B. brunnea
  26. B. burdettii - Burdett's Banksia
  27. B. caleyi - Cayley's Banksia, Red Lantern Banksia
  28. B. calophylla
  29. B. candolleana - Propeller Banksia
  30. B. canei - Mountain Banksia
  31. B. carlinoides
  32. B. catoglypta
  33. B. chamaephyton - Fishbone Banksia
  34. B. cirsioides
  35. B. coccinea - Scarlet Banksia, Waratah Banksia, Albany Banksia
  36. B. columnaris
  37. B. comosa
  38. B. concinna
  39. B. conferta - Glasshouse Banksia
  40. B. corvijuga
  41. B. croajingolensis
  42. B. cuneata - Matchstick Banksia, Quairading Banksia
  43. B. cynaroides
  44. B. cypholoba
  45. B. dallanneyi
  46. B. densa
  47. B. dentata - Tropical Banksia, Rilidili (Wubuy)
  48. B. drummondii
  49. B. dryandroides - Dryandra-leaved Banksia
  50. B. echinata
  51. B. elderiana - Swordfish Banksia, Palm Banksia
  52. B. elegans - Elegant Banksia
  53. B. epica
  54. B. epimicta
  55. B. ericifolia - Heath-leaved Banksia
  56. B. erythrocephala
  57. B. falcata
  58. B. fasciculata
  59. B. fililoba
  60. B. foliolata
  61. B. foliosissima
  62. B. formosa
  63. B. fraseri
  64. B. fuscobractea
  65. B. gardneri - Prostrate Banksia
  66. B. Giant Candles
  67. B. glaucifolia
  68. B. goodii - Good's Banksia
  69. B. grandis - Mangite, Bull Banksia, Giant Banksia
  70. B. grossa - Coarse Banksia
  71. B. heliantha
  72. B. hewardiana
  73. B. hirta
  74. B. hookeriana - Hooker's Banksia
  75. B. horrida
  76. B. idiogenes
  77. B. ilicifolia - Holly-leaved Banksia
  78. B. incana - Hoary Banksia
  79. B. insulanemorecincta
  80. B. integrifolia - Coast Banksia, White Honeysuckle
  81. B. ionthocarpa
  82. B. kingii (fossil)
  83. B. kippistiana
  84. B. laevigata - Tennis Ball Banksia
  85. B. lanata - Coomallo Banksia
  86. B. laricina - Rose Banksia, Rose-fruited Banksia
  87. B. lemanniana - Lemann's Banksia, Yellow Lantern Banksia
  88. B. lepidorhiza
  89. B. leptophylla - Slender Leaved Banksia
  90. B. lindleyana - Porcupine Banksia
  91. B. littoralis - Western Swamp Banksia, Swamp Banksia,
  92. B. longicarpa (fossil)
  93. B. lullfitzii
  94. B. marginata - Silver Banksia, Warrock
  95. B. media - Southern Plains Banksia, Golden Stalk Banksia
  96. B. meganotia
  97. B. meisneri - Meisner's Banksia
  98. B. menziesii - Menzies' Banksia, Firewood Banksia
  99. B. micrantha
  100. B. mimica
  101. B. montana
  102. B. mucronulata
  103. B. nana
  104. B. nivea
  105. B. nobilis
  106. B. novae-zelandiae (fossil)
  107. B. nutans - Nodding Banksia
  108. B. oblongifolia - Rusty Banksia, Dwarf Banksia
  109. B. obovata
  110. B. obtusa
  111. B. occidentalis - Red Swamp Banksia, Water Bush Banksia
  112. B. octotriginta
  113. B. oligantha - Wagin Banksia
  114. B. oreophila - Western Mountain Banksia
  115. B. ornata - Desert Banksia
  116. B. pallida
  117. B. paludosa - Swamp Banksia, Marsh Banksia
  118. B. pellaeifolia
  119. B. petiolaris
  120. B. pilostylis
  121. B. plagiocarpa - Dallachy's Banksia, Blue Banksia, Hinchinbrook Banksia
  122. B. platycarpa
  123. B. plumosa
  124. B. polycephala
  125. B. porrecta
  126. B. praemorsa - Cut-leaf Banksia
  127. B. prionophylla
  128. B. prionotes - Acorn Banksia, Orange Banksia
  129. B. prolata
  130. B. proteoides
  131. B. pseudoplumosa
  132. B. pteridifolia
  133. B. pulchella - Teasel Banksia, Dainty Banksia
  134. B. purdieana
  135. B. quercifolia - Oak-leaved Banksia
  136. B. repens - Creeping Banksia
  137. B. robur - Eastern Swamp Banksia, Swamp Banksia, Broad-leaved Banksia
  138. B. rosserae
  139. B. rufa
  140. B. rufistylis
  141. B. saxicola - Grampians Banksia, Rock Banksia
  142. B. scabrella - Burma Road Banksia
  143. B. sceptrum - Sceptre Banksia
  144. B. sclerophylla
  145. B. seminuda - River Banksia
  146. B. seneciifolia
  147. B. serra
  148. B. serrata - Saw Banksia, Red Honeysuckle, Old man Banksia
  149. B. serratuloides
  150. B. sessilis
  151. B. shanklandiorum
  152. B. shuttleworthiana
  153. B. solandri - Stirling Range Banksia, Solander's Banksia
  154. B. speciosa - Showy Banksia
  155. B. sphaerocarpa - Fox Banksia, Round-fruited Banksia
  156. B. spinulosa - Hairpin Banksia
  157. B. splendida
  158. B. squarrosa
  159. B. stenoprion
  160. B. strahanensis (fossil)
  161. B. strictifolia
  162. B. stuposa
  163. B. subpinnatifida
  164. B. subulata
  165. B. telmatiaea - Swamp Fox Banksia
  166. B. tenuis
  167. B. tortifolia
  168. B. tricuspis - Lesueur Banksia, Pine Banksia
  169. B. tridentata
  170. B. trifontinalis
  171. B. undata
  172. B. verticillata - Granite Banksia, Albany Banksia
  173. B. vestita
  174. B. victoriae - Woolly Orange Banksia
  175. B. violacea - Violet Banksia
  176. B. viscida
  177. B. wonganensis
  178. B. xylothemelia

Gallery

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References

External links


  1. ↑ Liber C (2004). "Really Big Banksias". Banksia Study Group Newsletter 6: 4–5. 
  2. ↑ Johnson, S (1992). "Multiple Flower Heads". Banksia Study Report 9: 58. ISSN 0728–2893. 
  3. ↑ Blake, T (1988). "Multiple Heads". Banksia Study Report 8: 2. ISSN 0728-2893. 
  4. ↑ "Phytophthora in forests and natural ecosystems". Second International IUFRO meeting. Murdoch University. Retrieved on 2006-06-26.
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