All you wanted to know about Haworthias, Gasterias and Astrolobas: Astroloba robusta

Astroloba robusta, Swartrivier

Astroloba robusta P.Reinecke ex Molteno, van Jaarsv. & Gideon F.Sm.

by Jakub Jilemicky and Steven Molteno

robusta: referring to the short, robust inflorescences and flowers.

Astroloba robusta is easily recognised by its hard, sharp, glossy-sheen leaves, which usually have white margins and keels. Some populations have white spots or tubercles on their leaves. Others are totally glabrous.

Astroloba robusta, near Klipplaat

Its flowers are however what make this entity truly distinct from its closest relatives (Astroloba foliolosa and congesta to the East). Unusually, the inflorescences appear in later winter (roughly May to October), and are robust and short. Likewise the sessile flowers on the inflorescences are similarly robust – with thick peduncles and long, flared floral bracts.

Flower of A. robusta, just W of Willowmore

This species has an extremely wide distribution – as far West as Matjiesfontein, to as far East as Steytlerville (and perhaps even further). In addition, Astroloba robusta extends northwards into the Great Karoo, and its northern limit is unknown. It is known near Nelspoort and at the foot of the Molteno Pass outside Beaufort West. However unconfirmed reports of it near Fraserburg in the Northern Cape, could indicate a far wider distribution. Local variation is interesting.

South of Laingsburg the plants are tiny - dwarfed, gracile and thin. Near Rietbron was reported a very large and robust population, almost like A. tenax var. moltenoi plants from Prince Alfred area. Plants from Klipplaat to Willowmore have attractive white edges to their leaves. In the area between Floriskraal Dam and Prince Albert are growing all sorts of unusual forms - possibly intermediate between pentagona and robusta. Unconfirmed is the situation around Graaff-Reinet, were can be found a very robust form of Astroloba foliolosa; there are also other records further inland from here, where it is unclear if the plants are robusta or foliolosa.

Distribution map

In cultivation, this species requires similar conditions to other Astrolobas, but appreciates an even dryer regime. It can be propagated by seed, subdivision or cuttings. Cuttings and offsets are extremely slow to root, and require several weeks in a cool shady spot before planting.