The Arnold Arboretum’s living collections are celebrated as one of the most comprehensive and best documented of their kind in the world. “Harvard’s Tree Museum,” like any other museum, requires unique oversight and management to ensure the long-term preservation of its collections. Governance of the collections is established by the institution’s Collections Policy, a document that plays a role in decisions including acquisition and disposal, documentation, and maintenance of the plants. Our curatorial procedures—including those related to records, nomenclature, mapping, inventory field checks, and plant labels—are the product of continuous refinement and have become models for other institutions. The Arnold Arboretum Expedition Tool Kit is a compilation of knowledge and experience from plant collectors for plant collectors and includes references to specific resources necessary for a successful expedition. Landscape and collections care at the Arboretum is carried out by an array of horticultural professionals under the guidance of a Landscape Management Plan. The living collections are dynamic, with new acquisitions entering the collection almost daily. Our system for propagation and distribution ensures that new material is successfully grown and that our collections are shared with like-minded botanical and horticultural institutions.