Recent forecasts predict temperatures in the high teens to low 20’s in the Portland metro area with the possibility of ice. On the couple (sometime several) times per season that this happens I have decided that it is worth my effort to wrap some of my plants. I limit this heroic effort to my phormium and to a couple of burgundy leaf cordyline that are starting to develop some pretty significant height.
I use frost cloth inexpensively purchased by the linear foot from a local nursery (Garden Fever and/or Portland Nursery) and secure the covering with clothes pins. It takes me about 15-20 minutes to wrap 2 cordyline and about 8 phormium.
While it is unlikely that these plants would be killed in all but our most extreme weather events; cold icy wind can do significant damage to the foliage such that I might wish it were dead. By taking the extra effort to protect these plants, they will almost certainly survive the winter but will also be among the most be striking plants in my garden – getting better year by year.