Whenever placing and breaking the large fern, a peony will very briefly appear. Sometimes, the peony stays from anywhere from half a second to two seconds. Occasionally, when you break the large fern, the particle effect generated will be that of the sunflower plant.
To recreate this bug:
Open Minecraft 1.8+
Place down a large fern. You may be able to catch the peony appearing.
Break the large fern. You may catch the peony appearing or notice the sunflower particle effect.