Euphorbia polyacantha Boiss.
Eng.: Fishbone-thistle, fish-bone cactus. Spa.: Cardón. Fre.: Euphorbe. Ara.: Sheet.
Monoecious shrub, fleshy, cactiform, spiny, glabrous, up to 0.6-1.2 m in height, highly branched from the base. Stems (2-4 cm diameter) erect, with 4-5(7) compressed angles, with rounded teeth or crenations and dark-grey callous and continuous margins. Spines (0.3-1(1.5) cm) arranged in pairs, widely divergent, often curved upwards, dark grey, born at continuous buds (sometimes it can have prickles, but little developed and deciduous). Inflorescences (3-5 mm, excluding the capsules) born in between the pair of spines, formed by 1-3 sessile cyathia and with broadly oval, obtuse and denticulate bracts. Cyathium (1.5-2 × 2.5-3 mm) with 5 nectaries and 5 lobes: glands are entire and transversely oblong, while the lobes are erect, broadly cuneate or transversely fimbriate. Ovary shortly pedicellate and glabrous, inserted in a narrowly trilobed calyx. Capsule (3-4 × 3.5-4.5 mm) subglobose, trilobulate, dark purple, inserted in the involucre. Seeds (1.5 × 1.3 mm), broadly ovoid, greyish, rugose, without caruncula.
Flowering:
June to November.
Fruiting:
August to December.
Habitat:
On rocky terraces and slopes at high altitude, usually above 1,000 m.
Distribution:
In NE African mountains, especially along coastal and subcoastal regions of the Red Sea, from Ethiopia and Eritrea to SE Egypt.
Conservation status:
Rare but widely distributed species, it is not considered threatened. Currently, it has not been assessed at a global level on the IUCN Red List of Threatened Species. In the updated red list of Egypt (Shaltout & Bedair, 2023) it has been considered as Data Deficient (DD). Cactiform euphorbias are included in Annex II of CITES.
