How to place instantiated prefab on ground?

Hi,

I have this code which basically creates a tree in front of the player when the user clicks:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SpawnTrees : MonoBehaviour
 {
    public GameObject tree;
     public float distance;
 
     void Start(){
 
     }
     //Vector3 playerPos = transform.position;
     //Vector3 playerDirection = transform.forward;
     float spawnDistance = 10;
 
     // Update is called once per frame
     void Update()
     {
         if (Input.GetMouseButtonDown(0)){
             Vector3 playerPos = transform.position;
             Vector3 playerDirection = transform.forward;
             Vector3 spawnPos = playerPos + playerDirection*spawnDistance;
             Debug.Log(spawnPos);
             Instantiate(tree, spawnPos, Quaternion.identity);
         }
     }
      
 }

This works fine. But the issue is that the trees are being created a little above the ground instead of directly on top of the ground. Can someone please help me fix this? thanks!