The nights are getting colder and if you live inland you should start lifting tender perennial plants such as cannas and dahlias. They should be dug up and placed in a box of just-damp compost in a cool, airy place.
Nearer the coast it should be sufficient to just cover the area above the roots with a thick layer of leaf mould or compost.
If you're not sure if a plant is going to survive, take extra precautions by taking a cutting or three; cut just below a leaf bud and push into a pot of compost up to half the length of the cutting. Keep the pot somewhere cool but protected from frost.