In the spirit of our “Green Gridirons” series (but just in case college football wasn’t your thing), the “Big Ten’s Eco Efforts” series highlights creative off-the-field sustainability efforts. Nebraska is the only state in the country that recognizes the last Friday in April as a civic holiday known as Arbor Day. Every year, businesses across the “The Tree Planter State” close down to allow folks to do just that–plant trees. The campus of the University of Nebraska-Lincoln has been marking the holiday for 40 years with a tree planting ceremony on campus where hundreds of trees are planted by students and faculty. The ceremony is part of Focus Nebraska, a week-long event that promotes environmental sustainability, awareness, engagement and activism, said Richard Sutton, professor of agronomy, horticulture and landscape architecture.