Any chance you tossed some papaya seeds in the pile some time ago? If so, you could have a batch of seedlings. (If not, please let me know.)
And if that's so, you'll need frost-free conditions to bring them to mature fruiting plants. If you want to try, here’s an informative site: http://www.tropicalpermaculture.com/growing-papaya.html

And this site says “Papayas thrive in USDA hardiness zones 9-11, which corresponds to minimum winter temperatures of 19℉ to 40ºF (-7℃ to 4ºC). They may be damaged or die if exposed to prolonged frost, and prefer climates that are warm throughout most of the year.” http://www.wikihow.com/Grow-Papaya.

You may want to contact the Maricopa County Extension Service Office for further details:  http://extension.arizona.edu/maricopa.