United States National Arboretum

What is United States National Arboretum?

The United States National Arboretum is a major botanical research facility located in Washington, D.C.. Established by Congress in 1927 and operated by the U.S. Department of Agriculture, the site spans 446 acres along the Anacostia River.¹

The arboretum serves as a center for horticultural research, maintaining an herbarium with over 650,000 specimens and a comprehensive botanical library. Its grounds feature more than 7,000 types of plants, including notable collections of azaleas, bonsai, camellias, hollies, apple trees, and conifersand-tree), and conifers.¹

Beyond its scientific mission, the arboretum is a public destination that houses the National Grove of State Trees and the original columns from the U.S. Capitol building.¹

What is the difference between an arboretum and a botanical garden?

The primary difference between an arboretum and a botanical garden lies in their focus and scope. An arboretum is a specialized collection dedicated to the cultivation and study of woody plants, specifically trees and shrubs. In contrast, a botanical garden is a broader institution focused on the culture, study, and exhibition of a wide variety of plants, often including herbaceous species, to illustrate their natural relationships and taxonomic order.²³⁴

These institutions are closely related, and their functions often overlap:

• Integration: An arboretum may exist as an independent entity or function as a specific section within a larger botanical garden.²³
• Scientific Purpose: Both are distinguished from public parks by their commitment to scientific and educational goals, such as maintaining labeled collections, herbaria, and research facilities.²⁴
• Design: While both may incorporate landscape aesthetics, their layouts are typically organized by scientific or geographic relationships rather than purely for recreational use.⁴

How are bonsai trees cared for and displayed?

Bonsai is the art of cultivating and training living trees or shrubs in containers to maintain a miniature, naturalistic form. Caring for these specimens requires a disciplined approach to horticultural maintenance.⁷¹

Care and Maintenance

• Pruning: To maintain their small size, bonsai require regular pruning of both branches and roots throughout the growing season. Nipping of new shoots helps refine the shape and density of the foliage.⁷
• Repotting: Trees must be repotted every one to five years, depending on the species and root growth. During this process, roots are gradually pruned to reduce the soil ball, allowing the tree to remain in a small, shallow container.⁷
• Watering and Nutrition: Water is typically provided daily. Liquid fertilizer is also used to support the plant’s health within its restricted environment.⁷
• Training: Branches are often trained into specific shapes by tying them with wire to mimic the weathered, gnarled appearance of trees found in nature.⁷

Display

Bonsai are typically hardy species kept outdoors, though they may be brought inside temporarily for appreciation. When on exhibit, they are oriented to show a specific “front” or viewing side. They are often displayed in earthenware pots chosen to harmonize with the tree’s color and proportion, frequently placed on small tables or stands.⁷

What is the purpose of an herbarium in scientific research?

An herbarium serves as a vital reference collection of dried, pressed plant specimens, often described as the “dictionaries” of the plant kingdom. These collections are essential to scientific research for several key reasons:

• Taxonomy and Systematics: Herbaria provide the comparative material necessary for plant taxonomy. They house “type specimens,” which serve as the definitive reference points for describing and naming species, helping researchers resolve taxonomic disputes and identify new or misidentified plants.⁹¹⁰¹¹
• Historical and Biogeographic Data: By documenting where and when plants were collected, herbarium sheets allow scientists to trace historical plant ranges, locate endangered species, and understand the original biodiversity of degraded habitats.⁹¹⁰
• Genetic and Morphological Research: Specimens provide a source of DNA for genetic analysis and pollen for palynological studies. They also support research in fields such as ecology, ethnobotany, and paleobotany.⁹¹⁰
• Permanent Record: If a species becomes extinct in the wild, herbarium specimens remain the only physical record of its former existence.¹¹