Yes, BLUEBONNET is a Scrabble word!

Letter values in Scrabble US: B 3, L 1, U 1, E 1, B 3, O 1, N 1, N 1, E 1, T 1.

Is it a valid word?

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

low-growing annual herb of southwestern United States (Texas) having silky foliage and blue flowers; a leading cause of livestock poisoning in the southwestern United States
a brimless dark blue Scottish cap with a flat top and a plume on one side

Also: buffalo clover, texas bluebonnet, lupinus subcarnosus.