When two-tall grass blocks are punched, they will occasionally drop a textureless entity called seeds. Also, if the bottom block of two-tall grass is punched it will momentarily appear as a peony and then drop the "double tallgrass" entity (which I am not quite sure if that is a bug or a new feature. I'm relatively certain you used to have to use shears to obtain the double tallgrass).
Dupe of MC-59258