lamb's ears vs red rattle

lamb's ears

noun
  • Stachys byzantina, an ornamental low-growing perennial related to betony with soft, silky hairs on the leaves which give it an attractive silvery-gray color. 

  • Used other than figuratively or idiomatically: see lamb, ear. 

red rattle

noun
  • Any of several plant species of the genus Pedicularis and others. 

  • Odontites vernus (red bartsia) 

  • Pedicularis palustris (marsh lousewort) 

  • Pedicularis flammea 

How often have the words lamb's ears and red rattle occurred in a corpus of books? (source: Google Ngram Viewer )