goat's-beard vs oyster plant

goat's-beard

noun
  • A yellow-flowered Eurasian plant, of the genus Tragopogon. 

  • A woodland plant of the family Rosaceae, Aruncus dioicus. 

oyster plant

noun
  • Tragopogon porrifolius (common salsify, vegetable oyster, purple salsify, Jerusalem star), cultivated for its light-skinned edible root 

  • Mertensia maritima (oysterleaf, sea lungwort, sea bluebell), native to Europe and North America with leaves said to taste like oysters 

  • Pseudopodospermum hispanicum (syn. Scorzonera hispanica, black salsify, black oyster plant), cultivated for its dark-skinned edible root 

  • Acanthus mollis (bear's breeches), native to the Mediterranean 

  • Tradescantia spathacea (formerly Tradescantia discolor) (oyster herb, boatlily, Moses in a basket, cradle lily, Moses in his cradle, Moses on a raft, Moses in the bulrushes, men in a boat, Moses-in-cradle, salsify) 

How often have the words goat's-beard and oyster plant occurred in a corpus of books? (source: Google Ngram Viewer )