using boundary conditions to dissipate waves

[brium]

I am trying to model insect vibrations in a plant, and my current road block is that I can't model the roots and some of the other parts of the plant. I am trying to figure out a way to apply a boundary condition to the main stem of my plant (where the stem meets the soil) that will model the roots. In the actual plant waves are never reflected back to the insect, so I need to make a boundary condition that will dissipate all waves that reach the point on the plant that has the boundary condition. Any ideas?