While landing the gyroplane, the pilot stated his "initial" flare at an altitude of 15 to 20 feet above the runway was normal. At 5 feet above the runway, the gyroplane ballooned and the pilot added power to recover. The gyroplane then yawed to the right. The pilot applied left rudder, but touchdown occurred prior to the gyroplane being aligned with the runway. The gyroplane's nose spun to the left when the main wheels touched down and the gyroplane rolled onto its right side.