Wikipedia
Rehmannia is a genus of six species of flowering plants in the order Lamiales, endemic to China.
The genus was included in the family Scrophulariaceae or Gesneriaceae in some older classifications. The current placement of the genus is in neither Scrophulariaceae s.s. nor Plantaginaceae s.l. (to which many other former Scrophulariaceae have been transferred). Earlier molecular studies suggested that its closest relatives were the genera Lancea and Mazus (Oxelman et al., 2005), which have been included in Phrymaceae (Beardsley & Olmstead, 2002). Subsequently it was found (Xie et al., 2009) that Rehmannia and Triaenophora are jointly the sister group to Lindenbergia and the parasitic Orobanchaceae. Recently, the latest classification of flowering plants, the APG IV, enlarged Orobanchaceae to include Rehmannia, making it the only other genus, along with Lindenbergia, to not be parasitic within the family.