Yes, DASHEEN is a Scrabble word!

Letter values in Scrabble US: D 2, A 1, S 1, H 4, E 1, E 1, N 1.

Is it a valid word?

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

edible starchy tuberous root of taro plants
herb of the Pacific islands grown throughout the tropics for its edible root and in temperate areas as an ornamental for its large glossy leaves
tropical starchy tuberous root

Also: taro plant, colocasia esculenta, taro root.

Not playable in Scrabble US: DALO, EDDA.