Definition of oyster plants:
(n) :
Pseudopodospermum hispanicum (syn. Scorzonera hispanica, black salsify, black oyster plant), cultivated for its dark-skinned edible root
(n) :
Tragopogon porrifolius (common salsify, vegetable oyster, purple salsify, Jerusalem star), cultivated for its light-skinned edible root
(n) :
Mertensia maritima (oysterleaf, sea lungwort, sea bluebell), native to Europe and North America with leaves said to taste like oysters
(n) :
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)
(n) :
Acanthus mollis (bear's breeches), native to the Mediterranean