Season’s Greenings opens on Thanksgiving Day and remains open every day, 10 a.m. to 5 p.m., through Jan. 5, 2020. Remember that 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 the 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.