# Arnold Arboretum

The Arnold Arboretum is a botanical research institution and free public park affiliated with Harvard University and located in the Jamaica Plain and Roslindale neighborhoods of Boston.
Established in 1872, it is the oldest public arboretum in North America. The landscape was designed by Charles Sprague Sargent and Frederick Law Olmsted and is the second largest "link" in the Emerald Necklace. The Arnold Arboretum's collection of temperate trees, shrubs, and vines has an emphasis on the plants of the eastern North America and eastern Asia, where Arboretum staff and colleagues are sourcing new material on plant collecting expeditions. The Arboretum supports research in its landscape and in its Weld Hill Research Building.

## History

The Arboretum was founded in 1872. It was established through land and financial gifts from Benjamin Bussey and James Arnold, with trustee George Barrell Emerson facilitating its creation. Harvard appointed Charles Sprague Sargent as the first director, who partnered with landscape architect Frederick Law Olmsted to design the grounds. A unique agreement with the City of Boston ensured public access through a 1,000-year lease.
In the late 19th and early 20th centuries, the Arboretum became a center for botanical research, with Sargent publishing The Silva of North America and launching Garden and Forest. Inspired by his travels to Japan, the Arboretum began decades of plant collection in East Asia, led by botanists like Ernest Henry Wilson.
The Great Depression and World War II paused international collecting, shifting focus to landscape preservation and public education. The mid-20th century brought innovations in plant cultivation, with the 1962 construction of the Dana Greenhouses supporting horticultural research.
Plant exploration resumed in the 1970s, particularly in China, with partnerships like the Sino-American Botanical Expedition. In 2011, the Weld Hill Research Building opened, advancing scientific study. During the COVID-19 pandemic, the Arboretum remained open as a vital public refuge.
In 2022, the Arboretum celebrated its 150th anniversary, reaffirming its mission of research, conservation, and free public access. Today, it continues to serve as a leading institution in botanical science and education.

## Status within Boston Parks and Harvard University

The Arboretum is privately endowed as a unit of Harvard University. The land was deeded to the City of Boston in 1882 and incorporated into the Olmsted-designed park system that would become known as the Emerald Necklace. Under the agreement with the city, Harvard University was given a thousand-year lease on the property, and the university, as trustee, is directly responsible for the development, maintenance, and operation of the Arboretum; the City retains responsibility for water fountains, benches, roads, boundaries, and policing. The annual operating budget is largely derived from the endowment, which is based primarily on private philanthropy and managed by the university. Other income is obtained through granting agencies and contributors. All Arboretum staff are University employees.

## Location

The Arboretum occupies 281 acres in the Jamaica Plain and Roslindale sections of Boston. The Visitor Center is located at the Hunnewell Administration Building at 125 Arborway. The Arboretum contains four notable hills: Bussey Hill, Peters Hill, Hemlock Hill, and Weld Hill. Of these, Peters Hill is the tallest at 240 feet (73 meters).

### Climate

The Arboretum is located in USDA hardiness zone 6b (0 to −5 °F; −18 to −21 °C).

## Collections

At present, the living collections include over 17,000 individual plants (including nursery holdings) belonging to 10,914 accessions representing 115 plant families and 417 genera; with particular emphasis on the ligneous species of North America and eastern Asia. Historic collections include the plant introductions from eastern Asia made by Charles Sprague Sargent, Ernest Henry Wilson, William Purdom, Joseph Hers, and Joseph Rock. Recent introductions from Asia have resulted from the 1977 Arnold Arboretum Expedition to Japan and Korea, the 1980 Sino-American Botanical Expedition to western Hubei Province, and more recent expeditions to China and Taiwan.
Comprehensive collections are maintained and augmented for most genera, and genera that have received particular emphasis include: Acer, Fagus, Carya, Forsythia, Taxodium, Pinus, Metasequoia, Lonicera, Magnolia, Malus, Quercus, Rhododendron, Syringa, Paulownia, Albizia, Ilex, Gleditsia and Tsuga. Other comprehensive collections include the Bradley Collection of Rosaceous Plants, the collection of conifers and dwarf conifers, and the Larz Anderson Bonsai Collection. Approximately 500 accessions are processed annually.
The Index Herbariorum code assigned to Arnold Arboretum is A and it is used when citing housed specimens even after integration with Orchid Herbarium of Oakes Ames (AMES) and Gray Herbarium (GH).

### Collections policy

The mission of the Arnold Arboretum is to increase knowledge of the evolution and biology of woody plants. Historically, this research has investigated the global distribution and evolutionary history of trees, shrubs and vines, with particular emphasis on the disjunct species of East Asia and North America. Today this work continues through molecular studies of the evolution and bio-geography of the floras of temperate Asia, North America and Europe.
Research activities include molecular studies of gene evolution, investigations of plant-water relations, and the monitoring of plant phenology, vegetation succession, nutrient cycling and other factors that inform studies of environmental change. Applied work in horticulture uses the collections for studies in plant propagation, plant introduction, and environmental management. This diversity of scientific investigation is founded in a continuing commitment to acquire, grow, and document the recognized species and infraspecific taxa of ligneous plants of the Northern Hemisphere that are able to withstand the climate of the Arboretum's 281-acre (1.14 km$^2$) Jamaica Plain/Roslindale site.
As a primary resource for research in plant biology, the Arboretum's living collections are developed, curated, and managed to support scientific investigation and study. To this end, acquisition policies place priority on obtaining plants that are genetically representative of documented wild populations. For each taxon, the Arnold Arboretum aspires to grow multiple accessions of known wild provenance in order to represent significant variation that may occur across the geographic range of the species. Accessions of garden or cultivated provenance are also acquired as governed by the collections policies herein.
For all specimens, full documentation of both provenance and history within the collection is a critical priority. Curatorial procedures provide for complete and accurate records for each accession, and document original provenance, locations in the collections, and changes in botanical identity. Herbarium specimens, DNA materials, and digital images are gathered for the collection and maintained in Arboretum data systems and the herbarium at the Roslindale site.

### Plant records

Plant records are maintained on a computerized database, BG-BASE (BG-BASE Inc.), which was initiated in 1985 at the request of the Arnold Arboretum and the Threatened Plants Unit (TPU) of the World Conservation Monitoring Centre (WCMC). Currently the Arboretum uses a suite of ESRI Desktop and Mobile GIS software applications to manage, analyze, query, capture, manipulate, and display geographic information. A computer-driven embosser generates records labels. All accessioned plants in the collections are labeled with accession number, botanical name, source information, common name, and map location.

### Nursery and greenhouse

The Dana Greenhouses located at 1050 Centre Street (with a mailing address of 125 Arborway), were completed in 1962. They comprise four service greenhouses totaling 3,744 square feet (347.8 square metres), the headhouse with offices, cold rooms, storage areas, and a classroom. Adjacent to the greenhouse is a shade house of 3,150 square feet (293 square metres), a 12,600 cubic feet (360 m$^3$) cold storage facility, and three irrigated, inground nurseries totaling approximately 1+1⁄2 acres (6,100 m$^2$). Also located in the greenhouse complex is the bonsai and penjing pavilion, where the Larz Anderson Bonsai Collection is displayed from the middle of April to the end of October.

### 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.

## Activities
### Research

State of the art facilities host researchers investigating a range of topics.

### Education

The Arboretum's education programs offer school groups and the general public a wide range of lectures, courses, and walks focusing on the ecology and cultivation of plants.

### Horticulture

A team of horticulturists, arborists, gardeners, seasonal employees, and summer interns maintain the grounds. A wide array of vehicles and modern equipment, are used in grounds maintenance. Full time staff, are members of AFL/CIO Local 615, Service Employees International Union (SEIU).

### 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:
   Of the thousands of flowering plants in the Arboretum, only one, the lilac, is singled out each year for a daylong celebration. On Lilac Sunday, garden enthusiasts from all over New England gather at the Arboretum to picnic and tour the lilac collection. On the day of the event, which takes place rain or shine, the Arboretum is open as usual from dawn to dusk.

### Publications

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 Archived 2019-04-23 at the Wayback Machine), 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 Conservation (CPC), and as an active member of the North American Plant Collections Consortium (NAPCC), it is committed to broadening and maintaining its holdings of: Acer, Carya, Fagus, Forsythia, Ginkgo, Stewartia, Syringa, and Tsuga for the purposes of plant conservation, evaluation, and research. The Arboretum is also a member of the North American China Plant Exploration Consortium (NACPEC).