From Sonic Retro
As with all variations of the move, it is activated by pressing the (GCN)/White (Xbox)/ (PS2/PS3)/Z (PC) button once the HUD charge gauge is full. Team Blast involves the three team members joining together to perform a powerful combo move, which destroys all enemies in the vicinity and can do a great deal of damage to bosses.
Amy and Cream bounce around on Big's umbrella while he is twirling it. They all pose causing an explosion of flowers that destroy all nearby enemies. This particular Team Blast is a dream for novice players. Once activated, the player gains invincibility, a barrier, and all characters get leveled-up one level. It also has a larger attack radius when compared to the other Team Blasts. Unlike the other Team Blasts, the after effects are not limited to the energy left in the gauge after usage. In Team Battles, the opposing team cannot switch to another formation for a short period of time after Flower Festival is used. Flowers appear above the affected character until it wears off.