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Tree to 25 m. Bark rough and scaly. Branchlets pale brown and pubescent to almost glabrous. Leaves in whorls of three to five, narrowly obovate to elliptic, 4–20 × 1–2.6 cm, upper surface dull green and pubescent, lower surface white and woolly, margins entire, apex obtuse or emarginate; petiole 0.4–1 cm long. Inflorescences 5–12 cm long, subtended by tomentose bracts 0.2–1 cm long. Flowers pale yellow; tepals 2.2–2.5 cm long, pubescent outside; style 2.7–3.2 cm long, straight or curved; old flowers falling quickly to reveal the ‘cone’. Follicles up to 60, narrowly elliptic, 0.7–1.5 × 0.3–1 cm, smooth and tomentose; follicles opening when mature, usually less than a year after flowering. Flowering January to July (Australia). George 1999. Distribution AUSTRALIA: from Proserpine, Queensland to Port Phillip Bay, Victoria. Habitat Coastal dunes and headland at sea-level to montane rain forest or cloud forest near the peaks of the Great Dividing Range. USDA Hardiness Zone 9. Conservation status Not evaluated. Illustration Rosser 1993, George 1996. Cross-reference K188.
The Banksia integrifolia species complex has been examined a number of times by taxonomists (Thiele & Ladiges 1994, George 1999, Evans et al. 2002). As currently defined, it includes three subspecies. A key to these, modified from Thiele & Ladiges (1994) and George (1999), is presented below.
Most adult leaves 17–26 mm wide
Most adult leaves 10–18 mm wide; New South Wales (New England National Park to Mt. Wilson); montane forest over igneous rock
Most leaves 4–10 cm long, ± flat, dull green above; New South Wales, Queensland, Victoria; coastal or low elevations over sedimentary rock
Most leaves 10–20 cm long, ± undulate, shining green above; Queensland (between Proserpine and Brisbane); coastal dunes or inland plains
White Mountain Banksia
This subspecies differs from typical B. integrifolia in that the adult leaves are longer (10–13 cm long), more or less acute, and four to five times longer than wide. When the leaves are dried they have a dull bronze colour (pale greyish green in subsp. integrifolia). The follicles are less likely to open spontaneously in subsp. monticola. Thiele & Ladiges 1994, George 1999. Distribution AUSTRALIA: New South Wales, between New England National Park and Mt. Wilson in the Blue Mts. Habitat Montane forest over igneous rock. USDA Hardiness Zone 8–9. Conservation status Not evaluated. Illustration George 1996; NTviii, NT157.
Banksia integrifolia (s.l.) is said to be tolerant of frosts to –6ºC (Moore 2004), although its subsp. monticola should be sought, as a high-altitude variant, for greatest levels of cold tolerance. Its stature is not affected by its habitat. Specimens at 1200–1400 m on the Dorrigo Plateau have been measured at 30 m tall with dbh of 119 cm, and elsewhere heights of up to 35 m have been recorded (Liber 2004). A collection (ETAZ 4) was made in 2000 by D. Hardman and A. Jackson from Barrington Tops, New South Wales. Specimens from this source are in cultivation at Wakehurst Place and Kew, and were distributed to other gardens in southern England. Some suffered frost damage in their early stages and are now growing as multistemmed shrubs; others that were undamaged are growing as single-stemmed specimens. Growth is rapid, most plants at Wakehurst Place averaging 3.5 m, and one exceptional specimen there is now 5 m tall, and has produced over 50 inflorescences since planting in 2002–2003 (D. Hardman, pers. comm. 2007). The plants at Kew are now 1.5–1.8 m, although some specimens in the open ground there are showing signs of chlorosis, with yellow leaves. The first inflorescences were produced outdoors in 2003 (Clennett 2004), and the plants are now flowering freely. The white underside to the leaves is striking, especially when they are ruffled by a breeze (D. Hardman, pers. comm. 2007).
Specimens unidentified to subspecific level are grown elsewhere in the United Kingdom (and are commercially available), including an 8 m tree at Tresco Abbey, and one very slow-growing individual in Southend (Johnson 2007). Undifferentiated Banksia integrifolia is cultivated in Californian gardens, and subsp. monticola is offered commercially there. According to Moore (2004), B. integrifolia is relatively tolerant of heavier soils, and tolerant of coastal exposure and drought when established. Subsp. compar (R. Br.) K.R. Thiele, from Queensland, is probably not very hardy in our area, but grows well in the Chelsea Physic Garden.