Yes, DARNEL is a Scrabble word!

Letter values in Scrabble US: D 2, A 1, R 1, N 1, E 1, L 1.

Is it a valid word?

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

weedy annual grass often occurs in grainfields and other cultivated land; seeds sometimes considered poisonous

Also: bearded darnel, lolium temulentum.