Euphorbia knuthii is a dwarf spiny succulent shrublet with a tuberous main root, which continues into a serpentine caudex, freely branched from the top. It is sometimes accompanied by a number of underground rhizomes. Knuthi have roots that are Tuberous and rhizomatous. The tuberous roots are very showy and in many plants in cultivation are often raised above the soil. In plants which have been raised from cuttings, these roots tend to be thinner, and are more branched, eventually producing huge masses of many roots. In seed raised plants, the roots tend to be much larger and tend to be less branching. Main stem (caudex): Partly buried in the ground, with a short or elongated neck merging with the fleshy root. From the central growing point, the caudex produces numerous crowded branches, which look like a bunch of apparently separate plants at the ground level. Branches: Tufted, simple or branched, initially erect, but more scrambling as they become longer, sinuate, 3-15 cm long (but often much more longer in cultivation) 3- 4-angled, up to 12 mm wide, glabrous, light-green with longitudinal grey-green stripes, but plants grown under very bright light may tend to produce additional reddish pigments. Angles with prominent tubercles up to 12 mm apart and 2-4 mm prominent, deltoid or the upper margins nearly truncate and the lower sloping. While the stems of plants in cultivation are seldom deciduous, it can be argued that this species is geophytic - with the majority of the plant (the tuberous roots) occurring underground, and (under conditions of extreme drought) the stems being shed to conserve water. Phenology: It blooms in mid to late summer and the seed capsules ripe about one month later.