Improvements to a grass system

I have been trying to make a grass rendering system that is as simple as possible, but this doesn't seem to be working that well, in the sense that it requires a lot of "unaccounted" ms to render and in general takes around 10-20ms just to render the grass. Here is my current code, improvements to the code would be nice, and I have tried simplifying it as much as I could:

     private Camera cam;
     public Mesh grassMesh;
     public Material grassMaterial;
     public int grassRadius = 25;
 
     private Bounds bounds = new Bounds(Vector3.zero,Vector3.one);
     void Update () {
         Plane[] frustumPlanes = GeometryUtility.CalculateFrustumPlanes(Camera.main);
         for (int x = -grassRadius; x < grassRadius; x++) {
             for (int y = -grassRadius; y < grassRadius;y++) {
                 Vector3 pos = new Vector3 (x * 1.5f, 0.5f, y * 1.5f);
                 bounds.center = pos;
                 if (GeometryUtility.TestPlanesAABB(frustumPlanes, bounds)) {
                     if (Vector3.Distance (transform.position, pos) < grassRadius) {
                         Graphics.DrawMesh (grassMesh, pos, Quaternion.identity, grassMaterial, 0);
                     }
                 }
             }
         }
     }