The Petal Dresden Plate is one variety of the Classic Dresden Plate Quilt Block that was so popular in the 30's and 40's. It is constructed using a combination of piecing and applique techniques.
The dresden plate can be created by splitting the design into four units along the 2 x 2 grid (as shown in the exploded version of the block below). Alternateively, the background can be one solid piece, with the entire dresden sewn together and stitched down with applique stitches. The smoothly curved edges of this variety of Dresden is a bit trickier to achieve than the "blade" version shown here.
A circle layer is often centered over the petals so that the unit more closely resembles a flower.
Below are some other variations of Petal Dresden Quilt Blocks.