The word undergrowths 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: 22
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (95 words)
dehorns, dehorts, detours, downers, drought, druther, ghosted, godsent, gourdes, grounds, groused, grouser, grouted, grouter, growers, growths, grunted, grunter, guerdon, gunshot, gunters, gurners, hornets, hungers, hunters, hurters, norther, outdrew, outgrew, redrugs, regrout, regrown, regrows, reshown, resound, rethrow, retours, returns, rewords, rewound, rhetors, rodents, rongeur, rotunds, roughed, roughen, rougher, rounder, routers, shorted, shorten, shorter, shotgun, shouted, shouter, shunted, shunter, snorted, snorter, snouted, sounder, strowed, surgeon, thonged, thorned, throned, thrones, throngs, thrower, thunder, tongued, tongues, tonsure, toughen, tougher, tourers, troughs, trouser, trudgen, trudges, turgors, turners, undergo, undoers, undrest, unhorse, unshoed, unsowed, unswore, wonders, wordnet, wounder, wronged, wronger, wrought