Jour. Fac. Art. Sci., Shinshu University 23(1): 61-67 (1988)
Studies on the Development of Black Brown Color in Rose Petals
Hitoshi Yasuda and Makoto Aoyama


Chemical and cytological investigations on the black brown color of rose petals were conducted using a cultivar Black Tea and some unnamed breeding lines, having the similar tinge in flower color.

  1. Cyanidin and pelargonidin were detected as the major anthocyanidins in the petals, using the thin layer chromatography.
  2. The ratios of pelargonidin to cyanidin contents in the petals were 1 to 1~10, estimated from the sizes of spots and shades of their colors on the chromatograms.
  3. Microscopic observations on the fresh epidermis stripped off from the petals provide the following evidences:
    (1) Central vacuoles showed an orange tone specific to pelargonidin glycosides.
    (2) Some blue spherical bodies were recognized in the cells. The treatment with 0.1% hydrochloric acid brought about the color change of the bodies from blue to orange, being followed by oozing out some orange sap from the bodies.
  4. The bodies were recognized microscopically as the homologous structures to the tannin body with the paraffin sections of epidermis, which were prepared by fixing in Kaiser's solution and stained with toluidine blue.

These results offered a new explanation that the black brown of petals such as Black Tea was given by the compound of two colors, one being orange of pelargonidin glycoside and the other being blue of the tannin body causing bluing effects in red petals.

CybeRose note: Roses like 'Black Tea', 'Léonidas' and 'Brown Velvet' reportedly lose the "blue" tint in summer heat, and become more ordinary in their orange or orange/yellow bicolor tints. Similarly, 'Erinerung an Brod' and 'Veilchenblau' are less "blue" when the season or soil is dry.

To the contrary, some of the orange Polyanthas are definitely more "blue" in hot weather. 'Golden Salmon', below, is an example from Aug. 7, 2000. Perhaps a different mechanism is involved.