When you set the sprite for 'MISC: Grass Clippings', ZC actually uses the tile one to the right.
[679] Grass Clippings
...No, the selected tile is used as well.
If you are still having this issue, send an example quest so we can look at it.
No, _L_'s right it does use both of them.
The tileset was set up so that the first tile was the grass clippings, and the second tile was a solid black tile, so I couldn't see the grass clippings when you cut them.