Yes, CARDOON is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, R 1, D 2, O 1, O 1, N 1.

Is it a valid word?

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

southern European plant having spiny leaves and purple flowers cultivated for its edible leafstalks and roots
only parts eaten are roots and especially stalks (blanched and used as celery); related to artichokes

Also: cynara cardunculus.