Particle system works on one object, but not duplicate??

I am making a simple iphone game where the user is controlling a car. When the car hits a tree, I am attempting to:

• Stop rendering the tree

• Play the particle system (mimic's tree exploding)

• Destroy tree after 1 second

My code was working fine, but when I attempted to duplicate the tree, the particle system plays (upon collision) intermittently, and only for the original tree. Any advice?? using UnityEngine; using System.Collections;

 public class colUpdate : MonoBehaviour {
 
     public float timeSince = 0f;
     //GameObject player = GameObject.Find ("Player");
     carMove carScript;
 
 
     // Use this for initialization
     void Start () {
         GameObject player = GameObject.Find ("Player");
         carScript = player.GetComponent<carMove> ();
     }
     
     // Update is called once per frame
     void Update () {
         timeSince += Time.deltaTime;
     
     }
     void OnTriggerEnter (Collider col) {
         //Car hits tree
         if (col.gameObject.name.Contains("tree")) {
             GameObject thisTree = GameObject.Find (col.gameObject.name);
             MeshRenderer rend = thisTree.GetComponent<MeshRenderer> ();
             ParticleSystem ps = thisTree.GetComponent<ParticleSystem> ();
             //Plays particle system
             ps.Play ();
             //Makes tree disappear
             rend.enabled = false;
             Destroy (col.gameObject, 1);
         }
         //Car on road
         if (col.gameObject.name == "OnRoad") {
                 carScript.maxSpeed = 0.3f;
                 carScript.accel = 0.01f;
         }
         Debug.Log ("Working!: " + col.gameObject.name);
         timeSince = 0f;
     }
 
     //Car off road
     void OnTriggerExit (Collider col){
         if (col.gameObject.name == "OnRoad") {
             carScript.maxSpeed = carScript.grassSpeed;
             carScript.accel = -0.01f;
         }
 
     }
 
 }