An old Euphorbia clandestina plant may not add so many leaves anymore when the new growth season arrives. Still, the imposing shape achieved over the many years of its life is a joy to see.

The stem is often club-shaped, thicker where new growth concentrates the succulence at the apex. Stem thickness is slightly reduced below the tip when the newest part moves up and the knob stays on top with leaf and flower production. In picture a series of stem bulges and constrictions indicates fluctuating fortunes during past seasons, reflected in oscillating stem thickness.

The patterned oblique rows of stem tubercles, where leaves had dropped off long ago, count among the remarkable geometric artwork performed naturally by plants. Euclid had more educational success than is sometimes realised.