Vetiver Roots in Greywater

Below are an example of roots in the greywater system.

While most Vetiver Grass when exposed to excessive water and nutrients tend to grow short roots, this particular clump in the front quadrant of the bathtub grows longer roots than the rest. It’s unexplained as to why as the other clumps do not, and the roots only run down this edge of the tub. Heat from sun, aeration along edge perhaps.