Why are pine trees planted in front of the grave?

Generally speaking, it is a kind of pine and cypress, and it has the wish of "sleeping".

The cypress is tall and straight, and its cold resistance is amazing. It has always been regarded as a symbol of justice, nobility, longevity and immortality. People in China often plant cypress, pine and willow. Next to the tomb, it symbolizes the immortality of the dead and the peace and happiness of the world.