Ask Mr. Smarty Plants

Mr. Smarty Plants learns something new every day, and today we learned there was such a thing as a semidwarf peach tree. We also learned that this tree is a smaller selection or cultivar of Prunus persica. There are a number of members of the Prunus genus in our Native Plant Database:   Prunus americana (American plum), Prunus caroliniana (Carolina laurelcherry), Prunus emarginata (bitter cherry), Prunus fasciculata (desert almond), Prunus pensylvanica (pin cherry), Prunus texana (peachbush) and Prunus virginiana (chokecherry), but, alas, no Prunus persica, peach, which is believed to have originated in China but, like most food plants, has been hybridized and grafted so many times there is no determining the real parentage. The Lady Bird Johnson Wildflower Center is focused on the use, protection and propagation of plants native not only to North America but to the area in which they are being grown, so we really can't help you. 

We did, however, find this website from eHow How to Grow Semidwarf Peach Trees, that can possibly give you some leads. Pima County, on the south central border of Arizona, is in USDA Hardiness Zones 8b to 10. We would recommend you contact the University of Arizona Cooperative Extension Office for Pima County, and see if they have some idea what is going on with your peach tree.