There are 12 11-letter words that start with 'blu'.
| bludgeoning | blueberries | bluebonnets | 
| bluebottles | bluegrasses | bluejackets | 
| blueprinted | blueshifted | bluetongues | 
| bluffnesses | blunderbuss | bluntnesses | 
Note: These 12 11-letter words that start with 'blu' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with blue, blun, blur, blus, blub, bluf, blud, blui, blum, bluc.
4-letter words start with 'blu' (3)