bonsai are held in the cold storage unit at temperatures slightly above freezing. Lilac Sunday The second Sunday in May every year is "Lilac Sunday". This is the only day of the year that picnicking is allowed. In 2008, on the 100th anniversary of Lilac Sunday, the Arboretum website touted: Associated collections The Arboretum's herbarium in Jamaica Plain holds specimens of cultivated plants that relate to the living collections (approximately 160,000). The Jamaica Plain herbarium, horticultural library, archives, and photographs are maintained in the Hunnewell building at 125 Arborway; however, the main portions of the herbarium and library collections are housed in Cambridge on the campus of Harvard University, at 22 Divinity Avenue. Publications The inventory of living collections is updated periodically and made available to sister botanical gardens and arboreta on request; it is also available on the Arboretum's website (searchable inventory ). Arnoldia, the quarterly magazine of the Arnold Arboretum, frequently publishes articles relating to the living collections. Publication of a journal targeting more scientific audience, Journal of the Arnold Arboretum, established in 1919 with Charles Sprague Sargent as editor-in-chief, was suspended in 1990, when it was incorporated into Harvard Papers in Botany (HPB). The 71 volumes are available online at the Biodiversity Heritage Library. The Journal of the Arnold Arboretum published "notes on trees and shrubs with descriptions of new species and their relationships, letters from correspondents, and notes on the vegetation of countries visited by officers and agents of the Arboretum." Other editors of the journal include Albert Charles Smith, Clarence Emmeren Kobuski, Bernice Giduz Schubert, and Carroll Emory Wood Jr. A Reunion of Trees by Stephen A. Spongberg (curator emeritus) recounts the history of the introduction of many of the exotic species included in the Arobretum's collections. New England Natives written by horticultural research archivist Sheila Connor describes many of the trees and shrubs of the New England flora and the ways New Englanders have used them since prehistoric times. Science in the Pleasure Ground by Ida Hay (former curatorial associate) constitutes an institutional biography of the Arboretum. Institutional collaborations The Arboretum maintains an institutional membership in the American Public Garden Association (APGA), Botanic Gardens Conservation International (BGCI), and the International Association of Botanical Gardens and Arboreta. Additionally, members of the staff are associated with many national and international botanical and horticultural organizations. The Arboretum is also a cooperating institution with the Center for Plant