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Photographer: B.R. Maslin
Photographer: B.R. Maslin
Photographer: B.R. Maslin
Botanical name
Acacia monticola x tumida var. pilbarensis
Description
Shapely shrubs 1.5-2.5 m tall. Bark pseudo Minni Ritchi at base of main stems (i.e.grey and peeling in irregular, narrowly oblong strips that are flat or shallowly recurved at each end, the underlying new bark light brown), grey and smooth on upper stems and branches. Branchlets glabrous or with very fine, straight, short, spreading hairs. Phyllodes oblong-elliptic, 3-7 cm long, 8-16 mm wide, straight, with sparse, straight, spreading hairs that disappear with age (indumentum very difficult to see without magnification), bright green; with 3 main longitudinal nerves more pronounced than the rest (the nerves free from each other and not confluent with margin at base of phyllodes), the intervening minor longitudinal nerves fine and parallel with some anastomosing; apex obtuse, mucronulate. Gland not prominent, situated on upper margin of phyllode 0-1 mm above pulvinus. Inflorescences a mixture of simple axillary spikes and short racemes; raceme axes 2-12 mm long and growing out at apex; peduncles 6-11 mm long, sparsely to densely hairy (the hairs short, straight and wide-spreading); spikes obloid to short cylindrical, 10-16 x 11-12 mm when fresh, bright light to mid-golden. Flowers 5-merous; calyx dissected for about ¼-½ its length. Pods and seeds not seen.
Characteristic features
Shrubs with pseudo Minni Ritchi bark at base of main stems. Branchlets glabrous or with very fine, straight, short, spreading hairs. Phyllodes short and broad (3-7 cm x 8-16 mm), obtuse. Inflorescences a mixture of simple axillary spikes and short racemes; peduncles with sparse to dense short, straight, spreading hairs; spikes obloid to short cylindrical, 10-16 mm long. Pods and seeds not seen.
Distribution and ecology
This rare putative hybrid occurs in northwest Western Australia where it is known only from only a few collections in the vicinity of Nimingarra Ridge (near the abandoned Shay Gap township). It grows on sandplains at the base of low rocky ridges.
Flowering and fruiting period
Judging from the few specimens to hand the flowering period would extend from about mid-June to early August. Pods have not been seen.
Taxonomy
The putative hybrid status of this entity is suggested by field observations and from a critical examination of herbarium material. It has been observed to co-occur (at a low frequency) in a roadside population of A. monticola and A. tumida var. pilbarensis at one locality, and is recognized by its pseudo Minni Ritchi bark, short spikes and morphology of its phyllodes. Acacia monticola has typical reddish brown Minni Ritchi bark that exfoliates in shavings that are strongly recurved at the ends to form scrolls down the stem; A. tumida var. pilbarensis does not have Minni Ritchi bark. Acacia trachycarpa also hybridizes with A. eriopoda and A. monticola in the Pilbara.
Conservation status
There is insufficient information at present concerning this entity to justify including it on the Department of Environment and Conservation's Declared Rare and Priority Flora List.