I don't find a "desert willow" in any of my western tree books, but there
are 20 gazillion willows and all of them cross pollinate,

That is why botanical names are so important. Desert willow, Chilopsis
linearis, has nothing whatever to do with willows. It belongs to the
Bignoniaceae. It is an attractive & interesting tree, and as I suggested
earlier, it can be used for bonsai. The main difficulty lies in finding a
suitable place to keep it during the winter.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)