Euphorbia aeruginosa Schweickerdt (1935: 205)

Bruyns, Peter V., Klak, Cornelia & Hanáček, Pavel, 2020, A review of the Euphorbia schinzii-complex (Euphorbiaceae) in southern Africa, Phytotaxa 436 (3), pp. 201-221 : 205

1. Euphorbia aeruginosa Schweickerdt (1935: 205) .

Type:— SOUTH AFRICA. Transvaal (Limpopo): Soutpan, Soutpansberg, 12 April 1934, Schweickerdt & Verdoorn 688 (lectotype K!, designated by Bruyns 2012: 225, isolectotype PRE!).

Discussion: —This species is characterized by its scarcely angled branches (i.e. tubercles hardly raised out of the surface) with a distinctive pale blue-green colour (said to resemble that of weathered copper, whence the name), short and fairly broad spine-shields which do not taper noticeably below the spines and the fairly long, copper-coloured spines ( Schweickerdt 1935, White et al. 1941). A small fifth spine is occasionally present at the base of the spine-shield. The female floret is ± sessile.

Euphorbia aeruginosa is best known from the northern slopes of the Soutpansberg, which lies in the northernmost portion of South Africa and is close to the border with Zimbabwe, but it is also recorded from the Blouberg and from the northern parts of the Waterberg ( Fourie 1989).

White et al. (1941) mentioned that they were unsure whether certain plants that had been observed in the Olifants River Valley in the Lydenburg district (± 150 km south of the Soutpansberg), between Chuniespoort and Malipsdrift, Steelpoort and Burgersfort, belonged to E. aeruginosa ( White et al. 1941: 742) or to E. schinzii ( White et al. 1941: Fig. 837). Some of these collections with rounded branches look superficially like E. aeruginosa , but there is much variation in this area from almost round-branched plants to others with clearly 4-angled branches. All these plants share a many-branched, bushy habit up to 0.5 m in diam., often with rhizomatous branches, ± continuous angles along the branches, narrowly elliptical spine-shields with small stipular prickles (± 0.5 mm long) and the female florets are raised on a pedicel 1−1.5 mm long. In particular, they do not have the copper-coloured spines that are typical of E. aeruginosa and the spines are also shorter than usual in E. aeruginosa . On this basis and because of the longer pedicel of the female floret, these are excluded from E. aeruginosa and are placed under the new name E. steelpoortensis .