The Apple Tree Spacing Calculator is a new, free application created to help commercial apple growers determine correct orchard tree spacing. When making these determinations, the calculator takes into account scion, rootstock, soil, irrigation, management, and expected tree height. Ron Perry and Jerry Hull, Michigan State University, and Jon Clements, University of Massachusetts, developed the application. The calculator is used in conjunction with the iPhone, but is available to anyone with Internet access. Visit www.apple.com/webapps/calculate/appletreespacingcalculator.html for more information. There is also a Web-based version at www.umass.edu/fruitadvisor/clements/appletreespacing.htm.