Oops, forgot part of the story!
After my dad 'removed' (forshadowing o_o) all of the Sedum sarmentosum, we were happy... for half a week. The plant just regrew from the dropped cuttings. So again and again, we tried stopping this sedum. even now, (or at least last time I checked, about a week ago? I think?) it's still there, but much smaller.
And that ends today's story time!