The House of York, whose emblem it was. The White Rose.
Cardinal de la Pole. (1500-1558.) White Rose of England.
So Perkin Warbeck or Osbeck was always addressed by Margaret of Burgundy, the sister of Edward IV. (*-1449.) Lady Catherine Gordon, given by James IV as wife to Perkin Warbeck, was called “The White Rose.” She married three times more after the death of Warbeck. The White Rose of Raby.
Cecily, wife of Richard, Duke of York, and mother of Edward IV. and Richard III. She was the youngest of twenty-one children.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894