Spawned tree not falling

**I have two scripts, one to give the full tree health (Tree Health), which when it reaches 0 spawns a chopped tree. This works correctly and as expected, but when the chopped tree is spawned, the top half of the tree does not fall over D:! I have applied a capsule collider, a rigid body and the script (Push Tree) to the part of the tree that should fall (the stump stays) but it doesn't seem to fall. I have also applied a capsule collider to the stump of the cut tree. Anyway, here are the two scripts (C#):

Tree Health:

 using UnityEngine;
 
 using System.Collections;
 
 public class TreeHealth : MonoBehaviour {

 public int Health;
 public GameObject FallenTree;
 public Camera myCamera;
 void Start () {
     myCamera = GameObject.FindObjectOfType<Camera>();
 }
 void Update ()
 {
     if(Health > 0)
     {
         if(Vector3.Distance(transform.position, myCamera.transform.root.transform.position) < 15f)
         {
             if(Input.GetKeyDown(KeyCode.Mouse0))
             {
                 Ray ray = new Ray(myCamera.transform.position,myCamera.transform.forward);
                 RaycastHit hit;
                 if(Physics.Raycast(ray,out hit,15f))
                 {
                     if(hit.collider.gameObject == gameObject)
                     {
                         --Health;
                     }
                 }
             }
         }
     }

     if(Health <= 0)
     {
         Health = 0;
         Destroy(gameObject);
         Instantiate(FallenTree,transform.position,transform.rotation);
     }
 }

}

And here is the Push Tree script I am presumably having problems with:

 using UnityEngine;
 
 using System.Collections;
 
 public class PushTree : MonoBehaviour {
 public float Force;
 public Camera MyCamera;

 void Start ()
 {
     MyCamera = GameObject.FindObjectOfType<Camera>();
     GetComponent<Rigidbody>().AddTorque(MyCamera.transform.right * Force,ForceMode.Impulse);
 }
 
 // Update is called once per frame
 void Update () {
 
 }

}

If no one can find the problem in this code then any suggestions about the prefabs would also be gladly appreciated! :)