The Collaborative International Dictionary of English v.0.48:

Flower-de-luce \Flow"er-de-luce"\, n. [Corrupted fr.
   fleur-de-lis.] (Bot.)
   A genus of perennial herbs (Iris) with swordlike leaves and
   large three-petaled flowers often of very gay colors, but
   probably white in the plant first chosen for the royal French
   emblem.
   [1913 Webster]

   Note: There are nearly one hundred species, natives of the
         north temperate zone. Some of the best known are Iris
         Germanica, I. Florentina, I. Persica, I.
         sambucina, and the American I. versicolor, I.
         prismatica, etc.
         [1913 Webster]