Yes, WALLFLOWERS is a Scrabble word!

Letter values in Scrabble US: W 4, A 1, L 1, L 1, F 4, L 1, O 1, W 4, E 1, R 1, S 1.

Is it a valid word?

WALLFLOWERS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of numerous plants of the genus Erysimum having fragrant yellow or orange or brownish flowers
perennial of southern Europe having clusters of fragrant flowers of all colors especially yellow and orange; often naturalized on old walls or cliffs; sometimes placed in genus Erysimum
remains on sidelines at social event

Also: cheiranthus cheiri, erysimum cheiri.