Banksia petiolaris

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Banksia petiolaris
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Order: Proteales
Family: Proteaceae
Genus: Banksia
Subgenus: Banksia subg. Banksia
Section: Banksia sect. Banksia
Series: Banksia ser. Prostratae
Species:
B. petiolaris
Binomial name
Banksia petiolaris
Range of Banksia petiolaris in green

Banksia petiolaris is a rare

Victorian state botanist Ferdinand von Mueller in 1864, and no subspecies are recognised. B.  petiolaris is one of several closely related species that will all grow as prostrate shrubs, with horizontal stems and thick, leathery upright leaves. Those of this species can be viable for up to 13 years—the longest-lived of any flowering plant recorded. It bears yellow cylindrical flower spikes, known as inflorescences, up to 16 cm (6+1⁄4 in) high in spring. As the spikes age, they turn grey and develop up to 20 woody seed pods, known as follicles
, each.

Insects such as bees, wasps and even ants can pollinate the flowers. B. petiolaris is nonlignotuberous, meaning it regenerates by seed after bushfire. B. petiolaris adapts readily to cultivation, growing in well-drained sandy soils in sunny locations. It is suitable for rockeries and as a groundcover.

Description

Banksia petiolaris is a prostrate shrub that can spread to a diameter of 2 metres (6+1⁄2 feet). Its thick stems grow horizontally on the ground and are covered in fine hair. The new growth is more densely covered with velvety orange brown hair. The large, leathery, upright leaves arise vertically on petioles up to 15 cm (6 in) high. The upper surface faces north and is inclined at around 15 degrees off vertical. The leaf blades can reach 60 cm (24 in) in length and 4 cm (1+1⁄2 in) wide. They are dull green with serrated margins and a white undersurface. Dead leaves remain on the plant.[1] Flowering occurs in late spring. The cylindrical inflorescences are yellow in overall colour and range from 9 to 16 cm (3+1⁄2 to 6+1⁄4 in) high. As the flower spikes age, they fade to a greyish colour, the old flowers persisting. Up to 20 woody seed pods, known as follicles, may appear on each spike. Covered with a fine grey fur, they are elliptical in shape and measure 2.8–3.8 cm (1+1⁄8–1+1⁄2 in) in length, and 1.5–2 cm (5⁄8–3⁄4 in) in width.[2]

The

embryonic plant), measuring 1.0–1.5 cm (3⁄8–5⁄8 in) long by 1.4–2.0 cm (1⁄2–3⁄4 in) wide, and a papery wing. One side, designated the outer surface, is deeply pitted and the other is brown and smooth. The seeds are separated by a sturdy dark brown seed separator that is roughly the same shape as the seeds with a depression where the seed body sits adjacent to it in the follicle. The first pair of leaves produced by seedlings, known as cotyledons, are cuneate (wedge-shaped) and measure 1.2–1.4 cm (1⁄2–9⁄16 in) long by 1.8–2.0 cm (11⁄16–13⁄16 in) wide. They are dull-green with a faint net-like pattern. The auricle at the base of the cotyledon leaf is pointed and measures 0.2 cm (1⁄16 in) long. The first pair of leaves to appear after the cotyledons are 3.5 cm (1+3⁄8 in) long and oval in shape, with 2–3 lobes or teeth on each side. The next set are 5 cm (2 in) long with 7–10 teeth.[3]

B. petiolaris is fairly uniform across its range, though plants may vary in leaf size. Its yellow flower spikes and white leaf undersurface distinguish it from other prostrate banksias.[3]

Taxonomy

Typical prostrate shrub habit

Banksia petiolaris was first described by Victorian state botanist

nomenclatural synonym is Sirmuellera petiolaris (F.Muell.) Kuntze, which arose from Otto Kuntze's unsuccessful 1891 attempt to transfer Banksia into the new name Sirmuellera.[8]

In his 1981 monograph on the genus, Australian botanist Alex George placed B. petiolaris in B. subgenus Banksia because its inflorescence is a typical Banksia flower spike shape, in B. section Banksia because of its straight styles, and Banksia series Prostratae, because of its prostrate habit, along with five other closely related species. George held it to be most closely related to B. blechnifolia.[3]

In 1996, botanists Kevin Thiele and Pauline Ladiges published an arrangement informed by a cladistic analysis of morphological characteristics. Their arrangement maintained B. petiolaris in B. subg. Banksia and series Prostratae. They found it to be basal (the earliest offshoot) to the other prostrate banksias.[7] Questioning the emphasis on cladistics in Thiele and Ladiges' arrangement, George published a slightly modified version of his 1981 arrangement in his 1999 treatment of Banksia for the Flora of Australia series of monographs. The placement of B. petiolaris in George's 1999 arrangement may be summarised as follows:[2]

In bud, cultivated in Sydney
Foliage
Banksia
B. subg. Banksia
B. sect. Banksia
B. ser. Salicinae (11 species, 7 subspecies)
B. ser. Grandes (2 species)
B. ser. Banksia (8 species)
B. ser. Crocinae (4 species)
B. ser. Prostratae
B. goodii
B. gardneri
B. gardneri var. gardneri
B. gardneri var. brevidentata
B. gardneri var. hiemalis
B. chamaephyton
B. repens
B. blechnifolia
B. petiolaris
B. ser. Cyrtostylis (13 species)
B. ser. Tetragonae (3 species)
B. ser. Bauerinae
(1 species)
B. ser. Quercinae (2 species)
B. sect. Coccinea
(1 species)
B. sect. Oncostylis (4 series, 22 species, 4 subspecies, 11 varieties)
B. subg. Isostylis (3 species)

Since 1998, American botanist

B. brevidentata.[13]

Distribution and habitat

Endemic to Western Australia, Banksia petiolaris is found near the state's south coast from the vicinity of Munglinup east to Israelite Bay,[2] concentrated in two disjunct ranges—an eastern one around Cape Arid National Park, and western one east of Scaddan. It is found in white sandy soils in kwongan or mallee heathland, but sometimes occurs with the taller B. speciosa. It is often locally common, with many populations over 100 plants in size.[14]

Ecology

Main article: Ecology of Banksia

Like many plants in Australia's Southwest, Banksia petiolaris is adapted to an environment in which bushfire events are relatively frequent. Most Banksia species can be placed in one of two broad groups according to their response to fire: reseeders are killed by fire, but fire also triggers the release of their canopy seed bank, thus promoting recruitment of the next generation; resprouters survive fire, resprouting from a lignotuber or, more rarely, epicormic buds protected by thick bark.[15] B. petiolaris and the related B. blechnifolia are in the former category—rapidly growing plants killed by bushfire and regenerating by seed—while the other prostrate species are slow growing resprouters.[3]

Like other banksias, B. petiolaris plays host to a variety of pollinators—insects such as bees, wasps and ants were all recorded in the 1988 The Banksia Atlas survey.[14]

An assessment of the potential

water mould Phytophthora cinnamomi, unlike many Western Australian banksias.[17]

Banksia petiolaris has the longest-lived leaves of any flowering plant so far recorded—a study published in 1992 recorded a lifespan of up to 13 years for a single leaf, while leaves of 10 years of age ably maintained their ability to photosynthesize compared with young leaves. The authors concluded that leaf longevity is advantageous in plants in nutrient-poor soils, as the loss of valuable nutrients in leaf loss is minimised (the leaves store much of a plant's nutrients).[1]

Cultivation

B. petiolaris is grown fairly commonly in Australian gardens, making an attractive prostrate groundcover or

germinate.[19]

References

  1. ^
    doi:10.1071/BT9920849
    .
  2. ^
    ISBN 0-643-06454-0
    .
  3. ^
    S2CID 196677407
    .
  4. ^ Mueller, Ferdinand J. H. von (1864). "Banksia petiolaris". Fragmenta Phytographiae Australiae. 4 (27): 109. Archived from the original on 19 March 2018.
  5. ISBN 0-207-17277-3
    .
  6. ^ Bentham, George (1870). "Banksia" . Flora Australiensis: Volume 5: Myoporineae to Proteaceae. London, United Kingdom: L. Reeve & Co. pp. 541–62.
  7. ^
    doi:10.1071/SB9960661
    .
  8. ^ "Banksia petiolaris F.Muell". Australian Plant Name Index (APNI), IBIS database. Centre for Plant Biodiversity Research, Australian Government. Retrieved 27 March 2018.
  9. doi:10.1071/SB97026
    .
  10. PMID 21665734
    .
  11. doi:10.1071/SB04015
    .
  12. doi:10.1071/SB06016
    .
  13. PMID 23957450
    .
  14. ^
    ISBN 0-644-07124-9
    . pp. 186–87
  15. doi:10.1071/BT9950283
    .
  16. S2CID 31990487
    .
  17. doi:10.1071/BT9850629
    .
  18. ISBN 0-85091-143-5
    .
  19. ISBN 0-643-09298-6
    .

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