Step back into a 19th-century Christmas with a visit this weekend to the Luther Burbank Home & Gardens. This historical landmark, where renowned horticulturist Luther Burbank lived and worked, is once again holding its Holiday Open House on Saturday and Sunday, Dec. 4 and 5, with tours of the home decked out for Christmas, special activities for children and unique gifts for holiday shoppers. Botanical illustrator Amber R. Turner will sign copies of her new book, “Eye Spy a Tree: Welcome to the Arboretum,” an introduction to the trees of Burbank’s downtown Santa Rosa property. Visitors can hop on Rosie the Trolley for free round-trip rides to the Handmade Holiday…