Does Timer.periodic need to be cancelled on widget unmount?

Question

I'm using flutter hooks, and using the Timer.periodic to do some processing in my widget.

Here's how I'm using it:

    final countdownStream = useMemoized(
      () => Timer.periodic(
        // ...
      ),
    );

Do I need to cancel this or will it automatically be removed? If I extract the Timer.periodic to a reusable function, what then?

Thanks