ah yeah, it grows back too quickly, we thought it had something to do with the pillar at the top
We have noticed through some gameplay videos, that when using the aim/power washer to clean, some clusters on the stone pillar look completely clean except for some hidden pixels.
We hope to release an update soon that addresses this issue. In the meantime, spraying the clusters without foliage, without aiming, seems to hit those pixels much easier.