Plants can serve as a profound symbol of friendship, especially when they cross an ocean to help two nations strengthen their bonds. I witnessed this firsthand on March 9, when I visited the Irish Embassy in Washington, D.C., joining Irish Ambassador to the United States Daniel Mulhall as he received a shipment of Ireland’s iconic shamrock plants. Embassy staff later arranged those shamrocks in an elegant, engraved crystal bowl for Irish Prime Minister Leo Varadkar to present to President Trump as a St. Patrick’s Day gift. That token of goodwill continued an annual tradition spanning 50 years.