Custom Taxonomy Hierarchy for Custom Post Types (eg Categories and Subcategories)

I’m working on building some custom taxonomies for a custom post type I created.

The custom post type is Products. For the custom post type Products I’ve created a taxonomy of Category. Now Under Category, I’d like to have a taxonomy of Sub_Category. I’ve created all the taxonomies and set them to hierarchical, but the Sub_Category tax seems to be relative to the Product Custom Post Type, NOT the Category custom taxonomy. Is there a way to do this? I saw a screenshot where someone was filling out a taxonomy form for a taxonomy they created and it had an option for PARENT but I could never get that to show up. How can I choose a PARENT Category taxonomy on my SubCategory taxonomy?

Here is my Category and SubCategory taxonomy code:

function create_productcategory_taxonomy() {
    $labels = array(
        'name' => _x( 'Categories', 'taxonomy general name' ),
        'singular_name' =>_x( 'Category', 'taxonomy singular name' ),
        'search_items' =>  __( 'Search Categories' ),
        'popular_items' => __( 'Popular Categories' ),
        'all_items' => __( 'All Categories' ),
        'parent_item' => null,
        'parent_item_colon' => null,
        'edit_item' => __( 'Edit Product Category' ),
        'update_item' => __( 'Update Product Category' ),
        'add_new_item' => __( 'Add New Product Category' ),
        'new_item_name' => __( 'New Product Category' ),
        'separate_items_with_commas' => __( 'Separate categories with commas' ),
        'add_or_remove_items' => __( 'Add or remove product categories' ),
        'choose_from_most_used' => __( 'Choose from the most used categories' )
        );

    register_taxonomy('tf_productcategory', 'tf_products', array (
        'label' => __('Product Category'),
        'labels' => $labels,
        'hierarchial' => true,
        'show_ui' => true,
        'query_var' => true,
        'rewrite' => array( 'slug' => 'product-category'),
        )); 
}

function create_product_subcategory_taxonomy() {
    $labels = array(
        'name' => _x( 'SubCategories', 'taxonomy general name' ),
        'singular_name' =>_x( 'SubCategory', 'taxonomy singular name' ),
        'search_items' =>  __( 'Search SubCategories' ),
        'popular_items' => __( 'Popular SubCategories' ),
        'all_items' => __( 'All SubCategories' ),
        'parent_item' => __( 'Main Category' ),
        'parent_item_colon' => ( 'Main Category:' ),
        'edit_item' => __( 'Edit Product SubCategory' ),
        'update_item' => __( 'Update Product SubCategory' ),
        'add_new_item' => __( 'Add New Product SubCategory' ),
        'new_item_name' => __( 'New Product SubCategory' ),
        'menu_name' => __( 'SubCategories' )
        );

    register_taxonomy('tf_productsubcategory', 'tf_products', array (
        'label' => __('Product SubCategory'),
        'labels' => $labels,
        'hierarchial' => true,
        'show_ui' => true,
        'query_var' => true,
        'rewrite' => array( 'slug' => 'product-subcategory'),
        )); 
}

add_action( 'init', 'create_productcategory_taxonomy', 0 );
add_action( 'init', 'create_product_subcategory_taxonomy', 0 );