Acacia mutabilis

The shrub typically grows to a height of 0.3 to 3 metres (1 to 10 ft). It is glabrous branchlets has caducous stipules and can have minute hairs often found within the phyllode axils. The green to green phyllodes have a linear to oblanceolate shape and are straight to incurved. The phyllodes have a length of 1.5 to 5.5 cm (0.59 to 2.17 in) and a width of 1 to 8 mm (0.039 to 0.315 in).^[1] It blooms from August to October and produces yellow flowers.^[2] The rudimentary inflorescences are found on two headed racemes that have an axes of 0.5 to 1 mm (0.020 to 0.039 in) in length. The spherical flower-heads contain 16 to 32 golden flowers and have a diameter of 4 to 5 mm (0.16 to 0.20 in). The seed pods that form after flowering are curved or a singular coil. The black pods have a length of up to 7 cm (2.8 in) and a width of 2 to 3 mm (0.079 to 0.118 in). The shiny black seeds within have an oblong shape and are 3 to 4 mm (0.12 to 0.16 in) in length.^[1]

The species was first formally described by the botanist Bruce Maslin in 1999 as part of the work Acacia miscellany. The taxonomy of fifty-five species of Acacia, primarily Western Australian, in section Phyllodineae (Leguminosae: Mimosoideae) as published in the journal Nuytsia. It was briefly reclassified as Racosperma mutabile in 2003 by Leslie Pedley then transferred back into the genus Acacia in 2006.^[3]

There are five recognised subspecies.

• Acacia mutabilis subsp. angustifolia
• Acacia mutabilis subsp. incurva
• Acacia mutabilis subsp. mutabilis
• Acacia mutabilis subsp. rhynchophylla
• Acacia mutabilis subsp. stipulifera

A. mutabilis is most closely related to Acacia halliana, Acacia merrallii, Acacia simmonsiana and Acacia nitidula.^[1]