An internet search yielded this brief history of Doubledecker Coneflower:
A German plantsman, Eugen Schleipfer found an Echinacea plant that looked very different from the others. After years of selection, a reliable seed strain with two tiered flowers resulted. A set of shorter petals rests on top of the cone while a "skirt" of longer, deep rose-pink petals emerge from the base of the cone. First year plants sometimes produce single flowers. From the second year forward, a high percentage of two tiered flowers appear with either a single or double set of petals. Occasionally, older plants produce single flowers.
I purchased this as a very small plant 3 years ago from a mail order company. It had only bloomed with single flowers the past two summers, so I was excited this year when I saw some pink flower petals beginning to sprout out of the center cone! I wanted to wait to photograph them until they were fully formed, but unfortunately by the time that happened the original flower was already beginning to brown, as you can see by the tips of the petals.
Less than half of the flowers on my plant exhibited the double flower characteristic, so it will be interesting to observe, next year and beyond....to see if a greater percentage of flowers will display this trait. I think perhaps this variety is still a little unstable, but 'Doppelganger' (it's German name) is an interesting plant, adding an unusual charm to the cottage garden.
Fun Fact: The word "echinacea" comes from the Greek word "echinos" meaning "hedgehog", referring to the flower's spiky central cone.