There are about 300 species of Thesium in Africa, Asia, Europe and South America, with 178 species occurring in southern Africa. Thesium is a large genus of Old World root-parasitic herbs of the family Santalaceae, with small, linear or scale-like leaves and nut-like fruits Thesium is the largest member of the Santalaceae, also known as the sandalwood family.

The genus name Thesium is derived from the Greek thes, meaning ‘a hired labourer’, referring to the simple appearance of these plants. The species name viridifolium is derived from the Latin viridis and folius meaning ‘green leaves’, referring to the bright green leaves of this species.

Thesium viridifolium is often confused with T. capitatum, but these two can be easily distinguished because T. viridifolium has a longer and narrower perianth tube than T. capitatum. Thesium viridifolium has shorter perianth lobes and the stamens arise higher up in the tube and the style is longer. Another distinguishing feature is that the perianth segments in T. capitatum are acuminately pointed, whereas in T. viridifolium the apex is shorter and not as sharply pointed. According to Levyns (1940), on the Cape Peninsula, T. viridifolium is restricted to the southern half of the Cape Peninsula and T. capitatum ranges from the summit of Table Mountain to the Cape Of Good Hope Nature Reserve.