PLEASE HELP!! Grow tree tall and short (Animation) Cannot reverse the growing animation

this is what im trying to achieve,

if i press the up-arrow, the tree grows taller (10 foot)

if i press the down-arrow, the tree grows shorter (1 foot)

now suppose it has grown 5 feet tall, on pressing the down arrow, how can i make it short by reversing the animation.

Here is my code:

using UnityEngine; using System.Collections;

public class PlayerManager : MonoBehaviour { Animator anim;

 void Start () 
 {
     anim = GetComponent<Animator> ();
 }

 void Update () 
 {

//--------------------------Expand---------------------------------------- if(Input.GetKeyDown(KeyCode.UpArrow)) { anim.SetInteger("State",1);
anim.enabled = true; }

     if(Input.GetKeyUp(KeyCode.UpArrow))
     {
         anim.SetInteger("State",0);    
         anim.enabled = false;
     }

//-------------------------Contract--------------------------------------- if(Input.GetKeyDown(KeyCode.DownArrow)) { anim.SetInteger("State",2);
anim.enabled = true; } if(Input.GetKeyUp(KeyCode.DownArrow)) { anim.SetInteger("State",0);
anim.enabled = false;

     }
         
 }

}

Note: The animation sprite i created is of the tree growing tall upto 19 frames.