Yes, TURTLEHEADS is a Scrabble word!

Letter values in Scrabble US: T 1, U 1, R 1, T 1, L 1, E 1, H 4, E 1, A 1, D 2, S 1.

Is it a valid word?

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

showy perennial of marshlands of eastern and central North America having waxy lanceolate leaves and flower with lower part creamy white and upper parts pale pink to deep purple

Also: shell-flower, snake-head, chelone glabra.

Not playable in Scrabble US: SHELLFLOWER.