Planting and sprinkling water on the grave

To place a branch or to plant something on the grave is not an established practice in Deen. If a plant grows on the grave on its own, then it should be left and should not be removed. It is not a Sunnah practice to sprinkle water over the grave every time one visits the graveyard. However, after burying the deceased, it is permissible to sprinkle water over the grave in order for the soil to be settled.

And Allah Ta'ala (الله تعالى) knows best.