Yes, LICHENS is a Scrabble word!

Letter values in Scrabble US: L 1, I 1, C 3, H 4, E 1, N 1, S 1.

Is it a valid word?

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

any of several eruptive skin diseases characterized by hard thick lesions grouped together and resembling lichens growing on rocks
any thallophytic plant of the division Lichenes; occur as crusty patches or bushy growths on tree trunks or rocks or bare ground etc.