Yes, QUILLWORTS is a Scrabble word!

Letter values in Scrabble US: Q 10, U 1, I 1, L 1, L 1, W 4, O 1, R 1, T 1, S 1.

Is it a valid word?

QUILLWORTS is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

any of several spore-bearing aquatic or marsh plants having short rhizomes and leaves resembling quills; worldwide except Polynesia