Dynamically Populate a Form With Site Title

I read this post but it talks about how to populate a field dynamically with user meta data.

http://www.gravityhelp.com/forums/topic/right-parameter-names-to-pre-populate-the-names-fields#post-14044

How would I call the site title or tagline/description?

Would this work if placed in functions.php? (param name is 'site_title')

add_filter('gform_field_value_site_title', create_function("", '$value = populate_sitetitle(\'site_title\'); return $value;' ));
function populate_sitetitle($meta_key){
    global $blog_title;
	return $blog_title;
}