You received great advice. Do want to endorse what was said about the ditch lilies AKA H. fulva It can be very aggressive. Great for erosion control, not so great for your bed. It reproduces via stolons or runners which is why it is so difficult to get rid of and why it is spreads so easily.
I have some out by my mail box in solitary confinement (surrounded on three sides by concrete or asphalt) that has so far kept them under control.
