Is it permissible to plant trees around the grave to protect it?

Question:
A questioner says: In our area, they place some trees on the graves after burial so that sheep do not approach the graves, and also so that the wind does not blow them away, likewise. So that the wind does not blow away the soil on the grave. Is this action permissible?

Answer:
No trees are to be placed on it, nor what he mentioned, but pebbles are to be placed on it. Pebbles are placed on it, as was placed on the grave of the Messenger of Allah (peace and blessings be upon him), and as was placed on the graves of the Companions. Pebbles are placed on it to prevent the scattering of soil and to prevent the soil from being eroded by the flood. Yes, it serves as a protection. Yes.