'Yuletide' is a vernalis hybrid, so it may not be on the same schedule as the japonicas which have their foliage growth spurt in the spring after they're done blooming. Having said that, most plants do seem to wait for the warmer spring temps before they risk putting out new growth.

Are you concerned about whether your plant successfully made it through some cold weather? If your plant got zapped by cold, it may take a little longer than usual to put out new leaf buds.

Good luck!