c++ Simple Class Question

I have a class called htable, when it reaches a certain size it will rehash itself. Heres the pseudo code:

/* Creates new table, and deletes old one. */
Htable Htable::htable_rehash(){
   make new Htable;
   add old values to new table;
        delete old table;
   return new Htable;
}

to call it I would say hashtable = hashtable .htable_rehash();

My question is this: do i need to free the memory in the old hash table in the class, or will it be deleted when i say table = table.rehash?

can we just come to a consensus that there are some circumstances where it would be prudent to handle memory management yourself and for that reason it's a good idea to understand the concept and it's implementation in your language, but generally it's okay to never touch the thing?