QR codes are two-dimensional barcodes that can be read by many cell phones and smartphones. The codes, which are small squares with black and white patterns, appear in a variety of places, such as magazine and newspaper ads. A QR code is used to encode some sort of information, such as text or a URL. Source: Cellphones.about.com.
100 trees around the Quad have had these QR codes placed on them. If you have a smart phone, you can download a free QR code reader from your App store to read these QR codes. Scanning one of these tree’s QR code will take you to a page on this website corresponding to the tree you are looking at.