Yes, WILLOW is a Scrabble word!

Letter values in Scrabble US: W 4, I 1, L 1, L 1, O 1, W 4.

Is it a valid word?

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

any of numerous deciduous trees and shrubs of the genus Salix
a textile machine having a system of revolving spikes for opening and cleaning raw textile fibers

Also: willow tree.