The word perennials is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 16
Highest Scoring Words With Friends™ Plays In The Letters
Seven Letter Word Alert: (32 words)
alpeens, alpines, ensnare, ensnarl, insaner, leaners, leapers, nailers, penners, pennies, pinenes, plainer, planers, planner, pleaser, praline, presale, realise, relapse, relines, renails, repanel, repeals, repiles, repines, replane, replans, replies, spaniel, spanner, spelean, spinner