Show the nearest category

I’ve been strolling around but I couldn’t find the answer.

My post is in the following categories : Forest > Tree > Bark
I would like to display <a href="linktobark">Bark</a> on single.php

The code below shows me ‘Forest’

<?php
	$category = get_the_category();
	echo $category[0]->cat_name;
?>

Changing this to $category[3] displays ‘Bark’ as wanted, but what about posts in the ‘Tree’ section?

Is there a way I can only show the youngest [?] category?

Thanks for helping me out, guys.