Thanksgiving Day through Jan. 5, 2020; 10 AM to 5 PM. Remember the best things in life are free: the fragrance of a freshly cut fir tree; the magic of holiday lights and sumptuous decorations and the delight of a child discovering a make believe world of model trains. This year’s Season’s Greenings explores botanic gardens from Hawaii to Maine. Free. 100 Maryland Ave. SW. usbg.gov. Seasonal Music at the Garden. Dec. 3, 5, 10, 12, 17, 19, 26 and 31; 6 to 8 PM. Free. 100 Maryland Ave. SW. usbg.gov.