Loudon's Arboretum Britannicum is the most important systematic study of hardy British trees and shrubs to have been published in the past two centuries, and arguably ever. Its greatest significance lies in the fact that it combined a comprehensive study of trees and shrubs with geographically founded histories of arboriculture, analysis of the importance of trees and shrubs in landscape gardening and full-length portraits of trees at different growth stages. Loudon's ideas concerning arboretums developed in various ways during the 1820s and 1830s in response to his experience of trees in various contexts, including private gardens such as his Bayswater villa, botanical and horticultural society gardens, and country estate collections. The significance of the Arboretum Britannicum and arboretum concept, manifest in various changing forms, can only be fully appreciated if examined in the context of British scientific culture and particularly cultures of natural history. The book must also be judged in terms of Loudon's other efforts to promote botany within gardening and horticulture, encouraging new audiences and practitioners amongst all social classes in the British Isles and Ireland. Scientifically-informed arboriculture and landscape gardening should not be merely the preserve of aristocracy, gentry and their agents as in the days of Humphry Repton.