How to make a gameObject active triggered by a collision of another?

I’m trying to get Flower4 game object to become active after the player rolls over Flower3.

void OnCollisionEnter (Collision my_collision){
		//print ("Collided with " + my_collision.collider.name);
		if (my_collision.gameObject.name == "Bee") {
			Debug.Log ("I'm A Bee!!");
		}

	
		if (my_collision.gameObject.name == "Flower1") {
			UnityEngine.SceneManagement.SceneManager.LoadScene ("Level_Two");
		}
		if (my_collision.gameObject.name == "Flower2") {
			UnityEngine.SceneManagement.SceneManager.LoadScene ("Level_Three");


			if (my_collision.gameObject.name == "Flower3") {
				(my_collision.collider.name == "Flower3"){ 
					gameObject.SetActive(true)}
			
					
				//if (my_collision.gameObject.name == "Flower4") {
				//UnityEngine.SceneManagement.SceneManager.LoadScene ("Level_Four");}

			}
		}
	}

I’m supposing that you logic making Flower 4 active is Line 15-17? Because if it is, it doesn’t make much sense to me. Typing gameObject.SetActive(true) just enables the object that this script is attatched to.

I would suggest making a public variable flowerFour for Flower 4 and using this code

if (my_collision.gameObject.name == "Flower3") {
            flowerFour.SetActve(true);   
}