2d Procedural terrain generation forest

Hi, I am currently working on a project where I want procedural world generation. My main problem is, how to spawn my trees on top of my grass blocks, because everything I tried becomes always weird like this;

Here is the script:

   using System.Collections;
     using System.Collections.Generic;
     using UnityEngine;
     
     public class Worldgeneration : MonoBehaviour
     {
         [SerializeField] int width, height;
         [SerializeField] int minStoneheight, maxStoneHeight;
         [SerializeField] GameObject dirt, grass, stone, tree;
         public Transform player;
         public int spawnPointX;
         public int spawnPointY;
         public int maxtreespawn = 0;
         
         
         public void Awake()
         {
             spawnPointX = Random.Range(0, 300); // for my playerspawn
             spawnPointY = Random.Range(70, 90); // for my playerspawn
     }
         
         
         
         void Start()
         {
         Generation();
             Vector3 spawnPosition = new Vector3(spawnPointX, spawnPointY, 0);
             player.transform.position = spawnPosition;
         }
         void Update()
         {
         }
         void Generation()
         {
             for (int x = 0; x < width; x++) //This will help spawn a tile on the x axis
             {
                 // procedural generation increase and decrease the height value and apply this to the 
                 // stonespawndistance
                 int minHeight = height - 1;
                 int maxHeight = height + 2;
                 height = Random.Range(minHeight, maxHeight);
                 int minStoneSpawnDistance = height - minStoneheight;
                 int maxStoneSpawnDistance = height - maxStoneHeight;
                 int totalStoneSpawnDistance = Random.Range(minStoneSpawnDistance, maxStoneSpawnDistance);
                 for (int y = 0; y < height; y++)//This will help spawn a tile on the y axis
                 {
                     if (y < totalStoneSpawnDistance)
                     {
                         spawnObj(stone, x, y);
                     }
                     else
                     {
                         spawnObj(dirt, x, y);
                     }
                     if (totalStoneSpawnDistance == height)
                     {
                         spawnObj(stone, x, height);
                     }
                     else
                     {
                         spawnObj(grass, x, height);
                     }
                     if(maxtreespawn < 50)
                     {
                         
 
 spawnObj(tree, Random.Range(0, width), height + 2);
                     maxtreespawn++;
                 }
             }
         }
     }
     void spawnObj(GameObject obj, int width, int height)//What ever we spawn will be a child of our procedural generation gameObj
     {
         obj = Instantiate(obj, new Vector2(width, height), Quaternion.identity);
         obj.transform.parent = this.transform;
     }
 
 }