Boston’s venerable, Frederick Law Olmsted-designed linear park system, affectionately known as the Emerald Necklace, is certainly a sight to behold year-round, especially as spring approaches. In recognition of the imminent change of seasons—or perhaps the approach of St. Patrick’s Day, take your pick—the beloved open spaces become green at night as well as day with the addition of emerald-tinged lighting at several spots throughout the city. Dubbed Lights in the Necklace, this brilliant exhibition adorns trees at four key locales through the end of March: Charlesgate Park near the Commonwealth Avenue Mall (pictured), the H.H. Richardson-designed Shattuck Visitor Center in the Back Bay Fens, the Jamaica Pond Boathouse and the Walnut Avenue entrance to Franklin Park. Spearheaded by the Emerald Necklace Conservancy with the help of the Boston Parks Department and Boston Public Works and honoring the Emerald Necklace’s tree caretakers, the Olmsted Tree Society, the display is an encore presentation of an idea that first came to life during the pandemic, and, just like spring itself, makes a very welcome return.