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.
vetony
noun
betony (Stachys officinalis)
How often have the words lamb's ears and vetony occurred in a corpus of books? (source: Google Ngram Viewer )