Banksia scabrella

Species of woody shrub in the family Proteaceae from Western Australia

Banksia scabrella, commonly known as the Burma Road banksia, is a species of woody shrub in the genus Banksia. It is classified in the series Abietinae, a group of several species of shrubs with small round or oval inflorescences. It occurs in a number of isolated populations south of Geraldton, Western Australia, with the largest population being south and east of Mount Adams. Found on sandy soils in heathland or shrubland, it grows to high and across with fine needle like leaves. Appearing in spring and summer, the inflorescences are round to oval in shape and tan to cream with purple styles. Banksia scabrella is killed by fire and regenerates by seed. Originally collected in 1966, B. scabrella was one of several species previously considered to be forms of Banksia sphaerocarpa, before it was finally described by banksia expert Alex George in his 1981 revision of the genus. Like many members of the Abietinae, it is rarely seen in cultivation; however, it has been described as having horticultural potential.

Banksia scabrella grows as a low shrub to in height and across, with a spreading habit. Its lateral branches are low and often rest on the ground. The small linear leaves measure 0.8 to 2.8 cm in length and 0.1 cm in width and are crowded along the stems. George recorded flowering as occurring in spring and summer (September to January), Flowers occur in "flower spikes", or inflorescences, made up of hundreds of small flowers, or florets, densely packed around a woody axis. Quite conspicuous, they are terminal (occurring on the ends of branches) or on short side branchlets. Round or oval in shape, the cream or tan inflorescences are high and wide. The individual flowers are light yellow or cream, with the styles and upper floral parts purple. The perianths measure , while the pistils in length and are curved at the apex. The inflorescences fade to grey as they age and the old flowers do not fall off. Up to 80 follicles develop on one spike, and remain closed until opened after a bushfire. Oval shaped, they measure in length, by high, and wide. They open to release a dark brown oval seed long, wide with a papery dark 'wing' wide. In 1996, botanists Kevin Thiele and Pauline Ladiges published an arrangement informed by a cladistic analysis of morphological characteristics. They retained George's subgenera and many of his series, but discarded his sections. Banksia ser. Abietinae was found to be very nearly monophyletic, and so retained. It further resolved into four subclades, so Thiele and Ladiges split it into four subseries. Banksia scabrella appeared in the third of these, initially called the "telmatiaea clade" for its most basal member. As with George's classification, B. lanata and two subspecies of B. leptophylla emerged as close relatives of B. scabrella, but there was some question over the relationships between all five forms in the clade. This clade became the basis for a new subseries Leptophyllae, which Thiele defined as containing species with "indurated and spinescent common bracts on the infructescence axes", and seedling stems which were densely arachnose (covered in fine hair). Early in 2007, Mast and Thiele initiated a rearrangement of Banksia by merging Dryandra into it, and publishing B. subg. Spathulatae for the taxa having 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, then B. scabrella is placed in B. subg. Spathulatae.

Banksia scabrella is found in two disjunct areas of scattered populations; the first discovered being southeast of the small town of Walkaway south of Geraldton, while a more populous cluster is found southeast of Mount Adams in Western Australia. It has been placed on the Declared Rare and Priority Flora List, where it is classified as a "Priority Four – Rare" taxon; although it is rare, it is not currently threatened by any identifiable factors. These taxa require monitoring every 5 to 10 years. Many stands are populous, and number over 100 plants. However, over half the known population of B. scabrella is found on road verges. B. scabrella is highly susceptible to Phytophthora cinnamomi dieback. Killed by fire, the species regenerates from seed afterwards. The region between Geraldton and Gingin is a rich one for Abietinae banksias, and nine species occur there. Despite this, there is little overlap in range and habitat; Banksia scabrella is unusual in its co occurrence with B. leptophylla. Burma Road Nature Reserve is one of the few protected conservation areas in its range; there, Banksia scabrella is found most commonly in (and forms a prominent part of) a mallee sedgeland, which is dominated by the cord rush Ecdeiocolea monostachya as a ground cover, and the mallee Eucalyptus eudesmoides as an emergent species. It is found occasionally in acacia scrub heath, and rarely in acacia thickets and banksia woodland. An assessment of the potential impact of climate change on this species found that its range is unlikely to contract and may actually grow, depending on how effectively it migrates into newly habitable areas.

Seeds do not require any treatment, and take 14 to 16 days to germinate. Rarely cultivated, Banksia scabrella flowers in 3 to 5 years from seed. Information is limited on its reliability, but it has been grown successfully in South Australia. It is fast growing but ultimately untidy in habit, and would benefit from regular pruning. Some forms in the wild have a more compact habit, and are more promising for horticulture.