Michelle Obama presents Letterman's Top Ten "fun facts about gardening" First Lady Michelle Obama appeared on CBS' "Late Show with David Letterman" on Tuesday night to present the Top Ten list. The turn on the late night show is in line with several media appearances she has made recently to promote her new book: "American Grown: The Story of the White House Kitchen Garden and Gardens Across America." The first lady last appeared on Letterman's show in March. Appearing from the Map Room of the White House this time, Obama presented the following "fun facts about gardening:" 10: Gardening was invented in 1822 by Albert Gardener. 9: Plant avocado, tomato, onions and cilantro together -- grow a guacamole tree. 8: Eggplants were originally cultivated for use as doorstops. 7: In his lifetime, the average American will eat half a radish. 6: The largest zucchini ever grown contained a Starbucks. 5: Later this year, the Supreme Court will finally rule on "tomato" vs. "tomahto." 4: If you have an actual green thumb, it might be scurvy. 3: Lettuce is 96 percent water and 4 percent lettuce. 2: The White House tool shed contains shovels, trowels and Weed Whacker One. 1: With enough care and effort, you can grow your own Barack-oli.