Photo from: Bárbol
These plants are bitter. In the Middle Ages they were used as purgatives. In England, the leaves were chewed to “clean the head.” Also they were used equally in food and in perfume.
In Al Andalus it was thought that all food items had a purpose and virtues. Pyrethrum was to make one happy. The fresh flower may be added to decorate dishes. Like cress, the leaves were an ingredient for salads and other dishes. The leaves and flowers were added to soups for flavoring. The taste is peppery, similar to tansies.
In 13th C Al-Andalus, pellitory was an ingredient for honey water. In southern Europe the root of it was used to make a paste applied locally as an irritant. In England it was an ingredient for Sauce Vert (Green Sauce). There pellitory was included in a medicinal bath to cure all ills especially coughing in foggy London.
[Anon/Anderson. 1962:65; Anón/Huici.1966:494:270-271:526:285; Benavides-Barajas. Alhambra. 1999:162; ES: Anon/Perry. Sep 5, 02:ftn 221; ES: Herbs. Oct 8, 02; ES: Medieval Spanish Chef. Cotofles. Posted Feb 9, ’13;-->
See blog titled Cotofles, published Feb 9, ’13 for Anón, Al-Andalus recipe titled Agua Miel (Honey Water), pp 270-271 which uses pellitory as a primary ingredient.
1 garlic clove
 The recipe was not tried for lack of available ingredients.
ANDERSON'S PUBLICATION OF ANÓN 15TH CENTURY COOKERY