Yes, TITHONIA is a Scrabble word!

Letter values in Scrabble US: T 1, I 1, T 1, H 4, O 1, N 1, I 1, A 1.

Is it a valid word?

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

any plant of the genus Tithonia; tall coarse herbs or shrubs of Mexico to Panama having large flower heads resembling sunflowers with yellow disc florets and golden-yellow to orange-scarlet rays

Also: mexican sunflower.