Verticality is officially the 2011 'it' trend in Chicago gardening. First, there's The Plant, a former meatpacking facility in Back of the Yards that's being converted into a vertical farm; then, there's the green wall inside Embassy Suites; and let's not forget the green wall that Ald. Reilly prescribed for 500 N. Lake Shore Drive. Now, a company has installed 26 aeroponic grow towers between terminals 2 and 3 at O'Hare Airport. (Aeroponics, for the uninitiated, is a process similar hydroponics in which the plant's roots are misted with water.) The lettuce and other vegetables grown inside O'Hare will be served at airport restaurants.