Common Reed

Phragmites australis is among the most widely distributed flowering plants on earth, found on every continent except Antarctica, and it behaves the same way everywhere: dense stands of tall canes rising two to four metres from saturated ground, topped by feathery purple-brown plumes in late summer.
It is specified deliberately for constructed wetlands, reed-bed treatment systems and bank stabilisation, where its appetite for nutrients and its dense rhizome mat are exactly the point. In an ornamental pond it is a mistake, because that same rhizome will take the whole thing.
The Common Reed is a functional wetland species for treatment systems and bank stabilisation, and it must always be planted with containment.