Banksia oblongifolia

Species of plant
Speciesbox
|name = Fern leaved banksia
|image = Banksia oblongifolia2 Georges River NP email. jpg
|image caption = Banksia oblongifolia, Georges River National Park
|status = LC
|status system = IUCN3.1
|status ref =
|parent = Banksia ser. Salicinae
|taxon = Banksia oblongifolia
|authority = Cav. though is generally less than high, with several stems growing out of a woody base known as a lignotuber. The smooth bark is marked with horizontal lenticels, and is reddish brown fading to greyish brown with age. New leaves and branchlets are covered with a rusty fur. The leaves lose their fur and become smooth with maturity, and are alternately arranged along the stem. Measuring in length and in width, the leathery green leaves are oblong to obovate (egg shaped) or truncate with a recessed midvein and mildly recurved margins, which are entire at the base and serrate towards the ends of the leaves. The sinuses (spaces between the teeth) are U shaped and teeth are 1–2 mm long. The leaf underside is whitish with a reticulated vein pattern and a raised central midrib. The leaves sit on 2–5 mm long petioles. Opening to a pale yellow after anthesis, the spikes lose their flowers with age and swell to up to high and wide, with up to 80 follicles. Covered with fine fur but becoming smooth with age, the oval shaped follicles measure long by 0.2–0.7 cm high (0.1–0.3 in) and wide.

First collected by Luis Née between March and April 1793, the fern leaved banksia was described by Antonio José Cavanilles in 1800 as two separate species from two collections, first as Banksia oblongifolia from the vicinity of Port Jackson (Sydney), and then as Banksia salicifolia from around Botany Bay. Derived from the Latin words oblongus "oblong", and folium "leaf", the species name refers to the shape of the leaves. Richard Anthony Salisbury had published the name Banksia aspleniifolia in 1796 based on leaves of cultivated material. but was unsure whether Salisbury's B. aspleniifolia belonged under the same name. into four series based on leaf properties. He followed Brown in using the name B. oblongifolia, and placed it in the series Salicinae. In 1870, George Bentham published a thorough revision of Banksia in his landmark publication Flora Australiensis. In Bentham's arrangement, the number of recognised Banksia species was reduced from 60 to 46. He declared B. oblongifolia referrable to, and a synonym of, B. integrifolia. Bentham defined four sections based on leaf, style and pollen presenter characters. B. integrifolia was placed in section Eubanksia. Botanists in the 20th century recognised B. oblongifolia as a species in its own right, but disagreed on the name. Those in Queensland felt Salisbury's name was invalid and used Banksia oblongifolia, while New South Wales authorities used Banksia aspleniifolia as it was the oldest published name for the species. Botanist and banksia authority Alex George ruled that oblongifolia was the correct name in his 1981 revision of the genus. After reviewing Salisbury's original species description, which is of the leaves alone, he concluded that it does not diagnose the species to the exclusion of others and is hence not a validly published name—the description could have applied to juvenile leaves of B. paludosa, B. integrifolia or even B. marginata. In this arrangement, B. oblongifolia is placed in Banksia subgenus Banksia, because its inflorescences take the form of Banksia's characteristic flower spikes, section Banksia because of its straight styles, and series Salicinae because its inflorescences are cylindrical. In a morphological cladistic analysis published in 1994, Kevin Thiele placed it in the newly described subseries Acclives along with B. plagiocarpa, B. robur and B. dentata within the series Salicinae. However, this subgrouping of the Salicinae was not supported by George. In 2007, Mast and Thiele rearranged the genus Banksia by merging Dryandra into it, and published B. subg. Spathulatae for the taxa having spoon shaped cotyledons; thus B. subg. Banksia was redefined as encompassing taxa lacking spoon shaped cotyledons. They foreshadowed publishing a full arrangement once DNA sampling of Dryandra was complete; in the meantime, if Mast and Thiele's nomenclatural changes are taken as an interim arrangement, B. oblongifolia is placed in B. subg. Spathulatae.

George noted that Banksia oblongifolia showed considerable variation in habit, and in 1987 Conran and Clifford separated the taxon into two subspecies. In examining populations in southern Queensland, they reported that the two forms were distinct in growth habit and habitat, and that they did not find any intermediate forms. However, George rejected the varieties, stating the variability was continuous. A possible hybrid between B. oblongifolia and B. integrifolia was recorded near Caloundra by Banksia Atlas volunteers. The Agnes Banks Woodland in western Sydney has been recognised by the New South Wales Government as an Endangered Ecological Community. Here B. oblongifolia is an understory plant in low open woodland, with scribbly gum, narrow leaved apple and old man banksia (B. serrata) as canopy trees, and wallum banksia (B. aemula), variable smoke bush (Conospermum taxifolium), wedding bush (Ricinocarpos pinifolius), showy parrot pea (Dillwynia sericea) and nodding geebung (Persoonia nutans) as other understory species.

Banksia oblongifolia plants can live for more than 60 years. These shoots are able to grow, flower and set seed two to three years after a fire. The woody infructescences also release seeds as their follicles are opened with heat, Older plants are serotinous, that is, they store large numbers of seed in an aerial seed bank in their canopy that are released after fire. The fungal species Asterina systema solare, Episphaerella banksiae and Lincostromea banksiae have been recorded on the leaves. A study of coastal heaths on Pleistocene sand dunes around the Myall Lakes found B. oblongifolia on slopes (wet heath) and B. aemula grew on ridges (dry heath), and the two species did not overlap. Manipulation of seedlings in the same study area showed that B. oblongifolia can grow longer roots seeking water than other wet heath species and that seedlings can establish in dry heath, but it is as yet unclear why the species does not grow in dry heath as well as wet heath. Unlike similar situations with Banksia species in Western Australia, the two species did not appear to impact negatively on each other.

Conrad Loddiges and his sons wrote of Banksia oblongifolia in volume 3 of their work The Botanical Cabinet in 1818, reporting it had been brought into cultivation in 1792, though had been initially and incorrectly called Banksia dentata. It flowered in November in the United Kingdom, and was grown in a greenhouse over winter. Not commonly cultivated, it adapts readily to garden conditions and tolerates most soils in part shade or full sun. The colours of the inflorescences in bud, and timing of flowers into winter give it horticultural value, as does its reddish new growth. Larger plants have taller flower spikes. It is propagated readily from seed, with young plants taking five to seven years to flower from seed. Pruning can improve the shrub's appearance, and it is a potential bonsai subject.