The stems of Monsonia crassicaulis are olive green when young and grey with age. The waxy stem covering renders it flammable. Stems reach a diameter of about 2 cm.
The leaves drop off in drought, leaving stems bare apart from the spines. New leaves grow at stem tips, from spine axils (on the upper stem parts) and at new spine tips.
In the Karoo this plant is in Afrikaans called the grootkersbos (big candle bush), distinguishing it from other Monsonia species with thinner stems (Vlok and Schutte-Vlok, 2010; Shearing and Van Heerden, 2008).