The dynastic kings of England from Henry II to Richard III, 1154-1485. 'Plantagenet' arose as the nickname of Count Geoffrey of Anjou (d. 1151), father of Henry II, apparently from his practice of sporting a sprig of broom (planta genista); another suggestion is that he favoured broom as cover in his hunting grounds. The plant was adopted as the family *crest. However, the use of the name dates from the 15c.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.