The lower, main stem of Euphorbia keithii loses side-branches and turns pale brown, rough and smooth patches seen all over. The old surface becomes thick and corky, bulging irregularly in places, dented in others, like barren land on a lifeless planet.
The vertical valleys down the trunk lie parallel as beds of once strong-flowing rivers. The occasional crater-like wound is present where one of the last, large branches had been attached long ago.
Instead of always growing one erect stem only, a few big branches may last, each ending in a rosette-like green cluster of small stem-tips and continually losing its lower branches, leaving a long bare section below.