Whenever you obtain one of the six alternate grass types, and attempt to get a pebble from it, nothing.
I tested this with all six types, no pebbles from any of them.
Botania: r1.9-335
Baubles: 1.10.2-1.3.0
Forge: 12.18.2.2106
Minecraft: 1.10.2 (obv)