Board Thread:Plants vs. Zombies 2/@comment-27557697-20150611135500/@comment-24275721-20150612194252

TheHandsomePlant wrote: Not really, we still don't exactly know what are boulder tiles for, and what plants/zombies do.

As far as I can guess, the boulder tiles are the opposite of Sun Tiles. The longer a plant is on them, the sun counter is deducted by 50 sun.

OR they block a space and doesn't let plants to be planted on them.