Esterhuysenia grahambeckii, a new rare succulent cliff-dwelling member of the Aizoaceae (Mesembryanthema) is described from the upper south facing cliff face of the Rooiberg, near Robertson (Western Cape). Unique features include its linear petals, 25–30 mm in length, remaining persistent on the plants for some time, capsules that remain open after their first opening, the capsule valves without wings and locules with erect covering membranes leaving their seeds exposed to the view from above.

Although its placement is somewhat uncertain it is here grouped in the genus Esterhuysenia, because it shares with the other five species the possession of a distinct mucro at the leaf tip. It is closest to Esterhuysenia stokoei from Dutoitskloof only in vegetative features, which include the soft textured leaves; however, the latter species differs in its smaller flowers, hygrochastic capsules and locules with covering membranes.