How to delete a state from the animator?

I’ve successfully made code that will add in a blendtree with the animations at set intervals that dynamically change dependent on how many motions are added. Where my code falls down is that it generates a new blend tree everytime it is called, which is everytime I press play.

Is there a way to alter this so that it deletes itself or changes itself instead of generating a new one?

public class AnimationSwitcher : MonoBehaviour
{
    public List<Motion> animations;
    public AnimatorController animator;

    private BlendTree blendTree;

    void Start()
    {
        
        animator.CreateBlendTreeInController("Active", out blendTree);
        addMotions();
    }


    public void addMotions()
    {

        int numberAnimations = animations.Count;

        for (int i = 0; i < animations.Count; i++)
        {
            Debug.Log(i);
            blendTree.AddChild(animations_, ((1 * i / numberAnimations)));_

}
}

}

Would wrapping your code in the Start function in an IF statement work? Only create the blend tree if one doesnt exist?