Warionia saharae has a light brown taproot, reminiscent of a parsnip. The youngest plants consist above ground of a rosette of oblanceolate, dentate leaves. Older plants develop stems, which are initially green but eventually become woody and develop a corky, grey bark. With about 75 μm, the diameter of the wood vessels is at the high end of the range within the Asteraceae. Wood fibers are relatively thick-walled. The wavy, somewhat fleshy leaves are set alternating along the stems, 2–13 cm long and 1–3 cm wide, oblong to oblanceolate. They are sinuate to pinnately partite, while the main vein in each lobe extends into an acute tip. The leaf is pinnately veined. While the leaf blade narrows at the foot, it still extends to the stem. The leaf surface is softly hairy with glandular hairs particularly near the edge.
