As far as I know (I didn't pond beyond a whiskey barrel when I lived there) all Tropical waterlilies are hardy in Phoenix.
I know Lynn is out in Mesa, she might chime in. If not, you might find her on the Arizona Gardening board at Garden Web.
Thanks LeeAnne, Lynn is a friend of mine.
A mutual friend manages to keep most of her lilies all winter. The difference is that she lives near a street with block walls around a smallish area. I live in an irrigated area and my pond is far from the street and we're a tiny bit higher than downtown Phx. There are no near block walls to hold the heat.
Timgod,
Are you asking for extreme heat temps or cold temps?
Anything that is viviparous is usually better suited to handle the cold. Many of mine bloom thoughout 10 months of the year.
As to heat, all tropicals love the heat but some fare worse than others.
Many of the multipetalled flowers without stamen don't like temps near or above 100 degrees.
King of Siam is an example of this.
Some do well as a fully grown and established plant but others look ugly in extreme temps.
I was asking about extremes in cold. I've already found out that the stamenless lilies don't like the heat in my pond.
I've had viviparous lilies that did indeed stand the cold water well. Unfortunately, they too have finally died out. They seem to last for a while, but eventually they can't make it through another winter. If we have an extended cold spell, like the winter of 2006/2007, they croak even faster. I had quite a bit of ice on my ponds this year, too.
The desert has extremes in temperature, many plants that can stand the heat, often can't take a cold winter.
