The species name is from the Latin armiger (bearing thorns or armed), in relation to its spiny phyllodes.

Fierce Wattle.

Dense, rounded, rigid, subglaucous shrub 0.8–1 m high, 1–2 m wide. Branchlets terete, smooth, with 2 rows of dense, minute, mostly patent to ascending hairs, glabrous to sparsely hairy between the rows of hairs, tardily glabrescent. Stipules seemingly absent. Phyllodes on short stem projections, rigid, patent to ascending, straight or shallowly curved, pentagonal in section with equal faces, 13–34 mm long, 1–1.2 mm diam., with a small patch of dense, white hairs at base on adaxial surface otherwise glabrous to subglabrous; longitudinal veins 5, scarcely raised, yellow when dry, no secondary veins in between; apex excentrically pungent-pointed with a long, fine, acicular point to 3 mm long; pulvinus absent; gland 1, occasionally absent from few phyllodes, elliptic, pit-like, c. 0.5 mm long, 8.5–13 mm above base of phyllode. Inflorescences comprising pedunculate, paired-axillary heads; peduncles (4.5–) 6–7.5 mm long, slender, glabrous or occasionally with sparse appressed hairs, subtended by a strongly cupped, caducous bract 1–1.4 mm long that is abaxially minutely pubescent; heads 3–4.5 mm diam. when dry, (13–) 17–23-flowered, bright yellow; bracteoles oblanceolate to spathulate, 0.7–0.9 mm long, glabrous. Flowers 5-merous; calyx c. half as long as petals, spathulate, the sepals free or very shortly united at base, glabrous; corolla 1.4–1.6 mm long, veinless, glabrous. Pods terete, 32–40 mm long, 2.5–3 mm wide, thick-crustaceous, curved, acute at both ends, sparsely appressed white-hairy, dark red (immature) maturing dark brown. Seeds longitudinal in pods; mature seeds not seen.

Dense, rounded, rigid, subglaucous shrub. Branchlets with 2 rows of dense, mostly patent to ascending hairs, glabrous to sparsely hairy between the rows of hairs; stipules seemingly absent. Phyllodes pentagonal in section with a yellow vein at each angle, rigid, straight or shallowly curved, 13–34 mm long, 1–1.2 mm wide, sessile; apex excentrically pungent-pointed. Inflorescences simple, globular, paired-axillary, on glabrous peduncles mostly 6–7.5 mm long; heads 3–4.5 mm diam. when dry. Flowers 5-merous; calyx c. half as long as petals, the sepals free or very shortly united. Pods terete, 32–40 mm long, 2.5–3 mm wide, with sparse, appressed, white hairs. Seeds longitudinally arranged.

Insufficiently known, but the type plant flowered in late August; young pods were also present at this time.

Native.

Known only from a single location near Mount Dimer, N of Southern Cross, Western Australia.

Tall open eucalypt woodland, in medium red-brown clay with a discontinuous pizolitic lag gravel, in a broad, non-incised drainage line. See Thiele et al. (2023) for associated species.

Listed as Priority One under Conservation Codes for Western Australian Flora (Western Australian Herbarium 1998–), as “A. sp. Southern Cross (G. Cockerton et al. WB 38518)”. The area where it occurs is relatively sparingly collected, and it is quite possible that the species is at least slightly more widespread than is currently known.

W.A.: [locality withheld for conservation reasons] 16 Oct. 2016, G. Cockerton, D. Brassington & D. Leach WB 38518 (PERTH).

Acacia armigera R.W.Davis, K.R.Thiele & Cockerton, Nuytsia 34: 95–98, fig. 1 (2023). Type citation: "Mount Dimer area, north of Southern Cross, Western Australia [precise locality withheld for conservation reasons], 31 August 2021, K.R. Thiele & G. Cockerton KRT 5719 (holo: PERTH 09457879; iso: CANB, MEL)".

Acacia sp. Southern Cross (G. Cockerton et al. WB 38518), Western Australian Herbarium, in FloraBase, https://florabase.dbca.wa.gov.au/ (accessed 17 May 2024).

Acacia armigera belongs to section Acacia and is most closely related to A. asepala which is readily distinguished by its glabrous branchlets, absence of sepals and flat pods that are 5–8 mm wide. It also morphologically similar to A. inamabilis and A. calcarata in having 5-veined, pungent, sessile phyllodes that are regularly pentagonal in section. However, those two species are readily distinguished by having persistent, spinose stipules, normally glabrous branchlets (occasionally hairy in A. inamabilis but hairs are evenly distributed over surface, not arranged in rows) and flat pods that are 5–10 mm wide.

K.R. Thiele et al., Nuytsia 34: 97, fig. 1 (2023).

Thiele, K.R., Davis, R.W. & Cockerton, G.T.B. (2023). Acacia armigera (Fabaceae), a new, geographically restricted wattle from the Coolgardie bioregion of Western Australia. Nuytsia 34: 95–98; https://doi.org/10.58828/nuy01048

Western Australian Herbarium (1998–). Florabase—the Western Australian Flora. (Department of Biodiversity, Conservation and Attractions); https://florabase.dbca.wa.gov.au/ [Accessed 27 March 2023]

Published 9 July 2024. Adapted from Thiele et al. (2023); PERTH specimens 2023.