Possible Clues:

• Plant manufactured old car - millions driven away
• Some of the very poor risk growing such a root
• Plant identified by Cockney writer of Latin Odes, say?
• Sort of iris that often takes root
• Any of various kinds of iris
• Minor risks with potted plant
• Poor grain's missing the odd root
• The alternative to the scent of the knight back there
• Old lace, made of gold or silver
• Root used in perfumes