Banksia grossa
Banksia grossa | |
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B. grossa north of Badgingarra
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Clade: | Angiosperms |
Clade: | Eudicots |
Order: | Proteales |
Family: | Proteaceae |
Genus: | Banksia |
Species: | B. grossa
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Binomial name | |
Banksia grossa |
Banksia grossa is a species of shrub in the family Proteaceae and is endemic to Southwest Australia. It is one of fourteen species of banksia of the series Abietinae, all of which bear predominantly cylindrical or oval inflorescences. Collected in 1965, it was first formally described in 1981 by Alex George. Its thick leaves and large seeds distinguish it from other members of the Abietinae, and are the basis of its species name.
Found in sand or sand over laterite among heath between Eneabba and Badgingarra in Western Australia, the species grows as a many-stemmed shrub to 1 m (3.3 ft) high with narrow leaves and oval brownish flower spikes up to 10 cm (4 in) high, composed of hundreds of individual flowers. Flowering occurs throughout the cooler months of March to September. Flower spikes develop woody follicles which bear the seeds. After bushfire, Banksia grossa regenerates from its woody lignotuber; bushfires also stimulate the release of seeds, which germinate after disturbance. Visitors to (and likely pollinators of) inflorescences include insects and a nocturnal mammal, the white-tailed dunnart.
Description
Banksia grossa grows as a bushy shrub, generally 0.7 to 1 m (28 to 39 in) high,[2] or occasionally up to 1.5 m (4.9 ft) high.[3] Its many stems rise from a woody lignotuber.[2] Young stems have a coating of woolly hairs, while older stems are covered in flaky pale brown bark. Borne on 3 to 5 mm long petioles, the somewhat fleshy leaves are needle-like. Although they are between 4 and 12 cm (1.5 and 4.5 in) long and only 2 to 3 mm wide, they are still thicker than those of other members of the series Abietinae. The margins of the leaves are straight with no teeth and rolled over, and the upper surfaces are sparsely hairy when young, but later hairless.[4] New growth occurs in the spring and early summer.[3]
Flowers
Flowers occur in a typical Banksia flower spike: an
Flowering occurs between March and September,[5] though early flowering in December has been recorded.[3] It takes five to eight weeks for a flower to develop from bud to the end of flowering. About three weeks before the flowers open, they develop a strong musky smell. The opening of flowers occurs sequentially, starting at the bottom of the inflorescence and sweeping through to the top over a period of around two weeks. At anthesis, the flowers produce copious quantities of nectar; indeed, some flowers produce so much that it drips to the ground.[5] After flowering, the old florets wither and curl against the spike, giving it a hairy appearance. Now known as an infructescence, it is roughly ellipsoidal, 6 to 10 cm high (2.2–4 in) and 4 to 8 cm (1.5 to 3 in) wide. Up to 25 smooth, elliptical follicles develop on the spike, each containing up to two wide wedge-shaped winged seeds.[4] One field study revealed, on average, eight follicles for each fertile cone.[6] Initially covered in fine fur, these are 2 to 4.5 cm (0.79 to 1.77 in) long, 1–1.8 cm (0.39–0.71 in) high and jut out by 1–1.8 cm (0.39–0.71 in).[2] The fur rubs off and they become smooth with wear, and generally remain closed until opened by fire.[2]
Seeds
The seeds of Banksia grossa are the largest of all the species of the series Abietinae. Measuring 2.8–3.9 cm (1.1–1.5 in) long, they are made up of a cuneate (wedge-shaped) seed body, 1.4–1.8 cm (0.55–0.71 in) long by 0.4–0.9 cm (0.16–0.35 in) wide, and a 2.7–3.3 cm (1.1–1.3 in) wide wing. The woody separator is the same shape as the seed, with an impression where the seed body lies next to it.[2] The bright green cotyledons are obovate and can be either convex or concave, measuring 1.6 to 2.2 cm long by 0.9 to 1.2 cm wide. These arise from a stocky seedling stem, known as the hypocotyl, which is reddish and covered in short hairs. The auricles of the cotyledons are 2 mm long. Seedling leaves arise 0.6 to 0.8 cm beyond the cotyledons and are oppositely arranged. Linear, they are 1.4 to 1.6 cm long with recurved margins and are covered in white hair. The stem remains reddish. Subsequent leaf pairs are successively longer.[2]
Taxonomy
The first known specimen collection of B. grossa was made by botanist
George's arrangement remained current until 1996, when
B. grossa | |||||||||||||||||||||||||
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This clade became the basis for the new subseries Sphaerocarpae, which Thiele defined as containing those species with lignotubers, styles loosely curling around the infructescence (although this trait was reversed in B. micrantha), and "transversely aligned cells of the seed wing inner face". The species other than B. grossa also have shouldered follicles.[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. grossa was the same as in 1981, except that B. telmatiaea was moved to set between it and B. leptophylla. The placement of B. grossa in George's 1999 arrangement may be summarised as follows:[4]
- Banksia
- B. subg. Banksia
- B. sect. Banksia (9 series, 50 species, 9 subspecies, 3 varieties)
- B. sect. Coccinea(1 species)
- B. sect. Oncostylis
- B. ser. Spicigerae (7 species, 2 subspecies, 4 varieties)
- B. ser. Tricuspidae(1 species)
- B. ser. Dryandroideae (1 species)
- B. ser. Abietinae
- B. sphaerocarpa (5 varieties)
- B. micrantha
- B. grossa
- B. telmatiaea
- B. leptophylla (2 varieties)
- B. lanata
- B. scabrella
- B. violacea
- B. incana
- B. laricina
- B. pulchella
- B. meisneri (2 subspecies)
- B. nutans (2 varieties)
- B. subg. Isostylis (3 species)
- B. subg. Banksia
Since 1998,
B. grossa | |
Early in 2007, Mast and Thiele initiated a rearrangement of Banksia by merging
Distribution and habitat
Banksia grossa mainly occurs from west of Yandanooka in the north, south to Badgingarra National Park, and east almost to Coorow. It grows in shallow sand over laterite, in deep sand, and occasionally atop lateritic rises, on flat or gently undulating land, among kwongan shrubland.[3][4] Around 40% of plants occur on road verges.[3]
Ecology
Banksia grossa resprouts from its woody lignotuber after bushfire. Shrubs carry relatively low numbers of seeds compared with plant species that regenerate by seed after bushfire. A field study in Eneabba showed shrubs bore anywhere from 30 to 90 seeds per plant. Seeds borne on plants, however, are less likely to be eaten by animals than seed lying dormant in the soil, and hence survive to produce future seedlings. Populations of resprouting plants, like B. grossa, benefit more from longer intervals between fires as their stored
The leaves of B. grossa are adapted to a dry climate. The lower surfaces are protected by the strongly revolute shape of the leaf, the leaf margins curling around underneath almost to the mid-vein. The trichomes (leaf hairs) run along the mid-vein and the margins, further protecting the surface where the stomates are located, thus minimising water loss.[13] Cladistic analysis suggests this species and its relatives in the series Abietinae developed long narrow leaves with inrolled margins as they invaded drier climates in Australia's southwest, having evolved from ancestors with broad leaves.[9]
The inflorescences are highly attractive to insects.[5] The rare bee species Hylaeus globuliferus is a recorded visitor.[14] Large numbers of ladybirds have been reported drinking the nectar of this species, while ignoring nearby Banksia attenuata inflorescences.[5] The white-tailed dunnart (Sminthopsis granulipes) has been observed visiting flower spikes. Pollen has been found on the snouts and in the scat of several species of dasyurid marsupials, which suggests these animals are likely pollinators of Banksia species in general.[15] No pollinators of this species were recorded in The Banksia Atlas survey.[3]
Banksia grossa is one of five closely related Banksia species that have highly unusual flower nectar.
Use in horticulture
Banksia grossa is cultivated for its attractive needle-like leaves and rusty-brown flower spikes, both of which can be quite variable in colour. This species favours well-drained sandy or loamy acidic soils with a pH of 5.5 to 7, and a sunny aspect. Once established, it tolerates dry spells. It can be pruned heavily as it resprouts from its lignotuber.[20]
Propagation is by seed.[20] The seeds do not require any treatment before sowing, and take around 14 days to germinate.[21] This is a slow-growing plant, taking 5 to 7 years to reach maturity and begin flowering.[20]
Cultural references
This banksia was featured on an Australian postage stamp in 2018.[22]
Notes
- ^ The other four species are Banksia sphaerocarpa, B. incana, B. leptophylla and B. telmatiaea.[16]
References
- ^ "Banksia grossa". Australian Plant Census. Retrieved 2 May 2020.
- ^ S2CID 196677407.
- ^ ISBN 0-644-07124-9.
- ^ a b c d e George, Alex S. (1999). Flora of Australia (PDF). Vol. 17B. Canberra: Australian Biological Resources Study, Canberra. p. 207. Retrieved 1 May 2020.
- ^ Lamont, Byron B.(1996). Why do Some Banksias Have Green Nectar?. International Symposium on the Biology of Proteaceae. Royal Botanic Gardens, Melbourne.
- ^ ISSN 1442-9993.
- .
- doi:10.1071/SB97026.
- ^ PMID 21665734.
- doi:10.1071/SB04015.
- ISSN 1030-1887.
- ISSN 1442-9993.
- ISBN 0-521-40197-6.
- ^ PaDIL. "Native globuliferus hylaeine". Australian Pollinators. Australian Government Department of Agriculture, Fisheries and Forestry. Retrieved 20 November 2012.
- ISSN 0004-959X.
- ^ S2CID 21719506.
- ^ Lamont, Byron B. (1980). "Blue-green Algae in Nectar of Banksia aff. Sphaerocarpa". West Australian Naturalist. 14 (7): 193–94.
- S2CID 39550788.
- ISSN 0067-1924.
- ^ ISBN 978-1-876473-68-6.
- ISBN 0-643-09298-6.
- ^ "Banksia grossa". Australian National Botanic Gardens. Retrieved 2 May 2020.