Different types of the same object

So, I'm in Xcode and programming a small program from a friend.

I want to initialize several instances of an object, put them in an array and then iterate through it (via a function that returns a string). Each object adds some text to that string when it's iterated, depending on the variables of the object.

Let's say the class is Tree. The variables in the class are name (string), height(int) and a hasLeaves(bool)(weather it currently has leaves on it or not). I could easily print:

"This is a name that is height meters tall and has leaves.

The problem is that I want the string to be a bit different, depending on which kind of tree it is. Like this:

The oak(name) is big and lifeful, it's height meters tall and has leaves.

Apple trees(name) carries some apples, it's height meters tall and has leaves.

If you ever visit Sweden you should check out the firs(name), they are height tall and haven't got leaves.

I don't want you to write the code for me, but give me a clue. I don't know what to look for. I was thinking about creating a subclass for each Tree, but every subclass would only appear once in the program and I don't know if it's necessary or not.

As you recognize, I'm having a hard time even formulating this question, but if you understand my intentions I'm glad for any clue I can get.

Edit: So this is my attempt to show it in code:

Class:

class tree {

var treeHeight: Int?
var treeWidth: Int?
var hasLeaves: Bool
var treeString: String


init (height: Int?, width: Int?, leaves: Bool, theString: String) {

    self.treeHeight = height
    self.treeWidth = width
    self.hasLeaves = leaves
    self.treeString = theString

    }

}

Main function:

var oak: tree = tree(height: 1, width: 2, leaves: true, theString:"Oh, the mighty oak")
var appleTree: tree = tree(height: 1, width: 2, leaves: false, theString: "Yummy Apples")

var treeArray: Array = [oak, appleTree]
var resultString = "This is the stories of the trees: "


for tree in treeArray {

        if tree.hasLeaves == true {

            resultString = resultString + tree.theString
            }

        }

So, I want the string added to the "resultString" to be different, depending on what kind of tree it is, but I don't want to set that string in the initialization of the object, but rather from what "kind" of tree it is. Does that make it easier to understand?

I want the string (treeString) to be static depending on what "kind" of tree it is. So if it is an oak, the string is always "Oh, the might oak".