|Banksia integrifolia subsp. var.||Coast Banksia|
Banksia integrifolia, commonly known as Coast Banksia, is a species of tree that grows along the east coast of Australia. One of the most widely distributed Banksia species, it occurs between Victoria and Central Queensland in a broad range of habitats, from coastal dunes to mountains. It is highly variable in form, but is most often encountered as a tree up to 25 metres (82 ft) in height. Its leaves have dark green upper surfaces and white undersides, a contrast that can be striking on windy days.
A hardy and versatile garden plant, B. integrifolia is widely planted in Australian gardens. It is a popular choice for parks and streetscapes, and has been used for bush revegetation and stabilisation of dunes. Its hardiness has prompted research into its suitability for use as a rootstock in the cut flower trade, but has also caused concerns about its potential to become a weed outside its natural habitat.
|Standard Cyclopedia of Horticulture|
Banksia integrifolia, Linn. Ten to 12 ft. : lvs. 6 in. long, 1-1½ in. wide, entire, or rarely a little dentate, the upper side dark green, silvery white beneath, scattered or sometimes irregularly verticillate; spikes 3-6 in. long; perianth about 1 in. long, greenish yellow.
Hardy and versatile, B. integrifolia will grow in clay, sand, acid and even alkaline soils, and it shows good resistance to wind and salt, making it suitable for seaside planting. It is therefore highly regarded as a low-maintenance garden tree, although its large size makes it unsuitable for smaller gardens. Its hardiness may however forewarn weed potential, as some evidence of weediness has been seen in Western Australia and New Zealand. When growing near bushland within its native habitat, it is recommended to obtain local provenance seed or plants if available.
The most common form available in commercial nurseries is unimproved Banksia integrifolia subsp. integrifolia. It prefers a sunny aspect without exposure to frosts, and tolerates fairly heavy pruning. Seeds do not require any treatment, and take 5 to 6 weeks to germinate. Flowering begins at around four to six years from seed. The other subspecies are less well known in cultivation, but are obtainable. Cultivation is presumably similar to B. integrifolia subsp. integrifolia, except that B. integrifolia subsp. monticola may be assumed frost-tolerant. Dwarf forms of B. integrifolia are sometimes sold, and a registered prostrate cultivar, Banksia 'Roller Coaster', is available. The latter is a vigorous ground-hugging plant that can spread to 4 or 5 metres across yet remains only 50 centimetres high.
Because of its high resistance to P. cinnamomi dieback, the feasibility of using B. integrifolia as a rootstock for susceptible Banksia species in the cut flower trade is under investigation. Presently, the success rate for grafting is only 30–40%, and even with successful grafts there is a tendency for the union to fail under stress. More research is needed before the technique will be ready for commercial use.
Pests and diseases
'Roller Coaster' has a prostrate form.
Although some of the great variability of B. integrifolia can be attributed to environmental factors, much is genetic: George writes that it "gives the impression that it is actively speciating to fill the many ecological niches through its range". Three subspecies are currently recognised: B. integrifolia subsp. integrifolia, B. integrifolia subsp. compar, and B. integrifolia subsp. monticola.
- Banksia integrifolia subsp. integrifolia
- The nominate subspecies occurs near the coast over most of the species' range except the far north. It varies little except in northern New South Wales and southern Queensland, where some populations appear to be intermediate with B. integrifolia subsp. compar.
- Banksia integrifolia subsp. compar
- This subspecies grows in coastal Queensland as far north as Proserpine. For most of its range it is the only subspecies, but near its southern limit it co-occurs with B. integrifolia subsp. integrifolia. The two subspecies are distinguishable by their leaves, which are larger and glossy with wavy margins on B. integrifolia subsp. compar.
- Banksia integrifolia subsp. monticola
- Commonly known as White Mountain Banksia, it is the only subspecies with a montane distribution; it occurs in the Blue Mountains of northern New South Wales. It is similar in form to B. integrifolia subsp. integrifolia, but differs in having longer, narrower leaves, and follicles that are more deeply embedded in the old flower spike.
Presumed natural hybrids have been reported between B. integrifolia and other members of Banksia ser. Salicinae, although no hybrid names have been formally published to date. Presumed hybrids are identified by their intermediate features; for example those with B. paludosa (Swamp Banksia), known from Jervis Bay and Green Cape on the coast of southern New South Wales, have a smaller habit, longer, thinner flower spikes, and persistent old flowers on old "cones", which are otherwise bare on pure B. integrifolia.
Presumed hybrids with B. marginata (Silver Banksia) occur on Wilsons Promontory in Victoria; these are found in localities where both species co-occur, and have features intermediate between the two. Another purported hybrid with B. marginata, thought to be from Cape Paterson on Victoria's south coast, was first described by Alf Salkin and is commercially available in small quantities. It forms an attractive hardy low-growing plant to 1 metre.
- ↑ Elliot, R. and D. L. Jones (1982). Encyclopaedia of Australian Plants Suitable for Cultivation. Melbourne: Lothian Press. ISBN 978-0-85091-143-5.
- ↑ Liber, C. (2002). "Banksias as weeds". Banksia Study Group Newsletter 4 (1): 4–5.
- ↑ Sweedman, Luke; et al. (2006). Australian seeds: a guide to their collection, identification and biology. CSIRO Publishing. p. 203. ISBN 0-643-09298-6.
- ↑ Template:The Banksia Book
- ↑ Australian Cultivar Registration Authority. "Banksia 'Roller Coaster'". Descriptions of registered cultivars. Retrieved on 2006-11-07.
- ↑ Sedgley, Margaret (1996). "Banksia, Family Proteaceae". in Krystyna A. Johnson and Margaret Burchett (eds). Native Australian Plants: Horticulture and Uses. Sydney: University of New South Wales Press. pp. 18–35. ISBN 978-0-86840-159-1.
- ↑ Cite error: Invalid
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- ↑ Harden G. J., D. W. Hardin and D. C. Godden (2000). Proteaceae of New South Wales. UNSW Press. ISBN 978-0-86840-302-1.
- ↑ Liber, C. (2005). "Banksia paludosa paludosa in the Jervis Bay Area" (PDF). Banksia Study Group Newsletter 6 (2): 4–5. http://asgap.org.au/banksSG/banksiasg-6-2.pdf. Retrieved 2006-10-31.
- ↑ Salkin, Alf I. (1979). Variation in Banksia in Eastern Australia. Thesis. Monash University.
- ↑ Liber, C. (2004). "Banksia integrifolia x paludosa hybrids at Green Cape" (PDF). Banksia Study Group Newsletter 6: 8–9. http://asgap.org.au/banksSG/banksiasg-6-1.pdf. Retrieved 2006-10-31.
- ↑ Salkin, Alf (1986). "Banksia Cultivars". Banksia Study Report (ASGAP) (7): 17–19. ISSN 0728-2893.
- Standard Cyclopedia of Horticulture, by L. H. Bailey, MacMillan Co., 1963