What is an Arboretum?

The Morton Arboretum

An arboretum is an outdoor living tree museum.
An arboretum is a botanical garden specializing in trees. Arboreta across the globe practice scientific research, promote conservation, and engage in public outreach and education to protect and preserve trees.

The Morton Arboretum has been the champion of trees since it was founded in Lisle, Illinois in 1922 by Joy Morton, president and founder of Morton Salt. The Arboretum encourages the planting and conservation of trees and other plants for a greener, healthier, and more beautiful world. Like other arboreta, it collects, studies, grows, shares knowledge about, and ultimately protects trees.

The inspiration for the Arboretum had its origins in Morton’s own family tree. His father, J. Sterling Morton (1832–1902), was the founder of the original Arbor Day in America. The founding documents require the Arboretum to maintain living collections, a research library, and an herbarium—all of which continue to be important parts of the mission.

Arboreta use living collections to learn about and conserve trees.

Living collections at an arboretum can be defined as trees that are grown with a purpose. Scientists and researchers can study these trees, learn how they grow, and understand what it takes to keep them safe and healthy. Further, these collections of trees can serve as stored genetic diversity.

Modern-day plant hunters help arboreta improve their collections.
Plant hunters travel the world tracking down and collecting live plants, seeds, and other material. The Morton Arboretum’s plant hunters partner with conservationists around the world to find, document, and collect threatened trees. The material and knowledge they bring back help conserve both tree diversity and genetic diversity within a species.

The Morton Arboretum’s curator and head of collections hunted plants throughout the southern United States, collecting acorns from oak species such as the endangered Oglethorpe oak (Quercus oglethorpensis), the endangered Georgia oak (Quercus georgiana), Boynton sand post oak (Quercus boyntonii), and Arkansas oak (Quercus arkansana). The material he collected will be shared with gardens and arboreta to increase the genetic diversity of their oaks.

Researchers also collect herbarium specimens during their time in the field.

Herbarium specimens are plants that have been pressed, dried, identified, and accessioned into a museum collection. Each preserved specimen is labeled with information about where and when it was collected. These specimens capture unique information about species ecology and form. As libraries of biodiversity, herbaria are essential to understanding how plant populations and species distributions change over time.

Herbarium specimens serve as a road map back to populations, allowing researchers to revisit the same sites years later to see if those trees are still present or if the plant community has changed.

Living collections can be organized in different ways.
Trees in living collections can represent diversity from different parts of the world or from different scientific plant groups. For example, Asia has a high diversity of plants. The Morton Arboretum began collecting trees from China in 1925. The resulting geographic collection is the most diverse in the Arboretum, with over 408 different kinds of trees, shrubs, vines, and herbaceous plants.

Trees can also be organized by scientific plant groups. This is an effective way to compare related plant species first-hand.

The Morton Arboretum has five champion collections: oak (Quercus), elm (Ulmus), maple (Acer), magnolia (Magnolia), and crabapple (Malus). Trees in these collections are curated, or chosen, by experts. These collections have high conservation value because they include genetic diversity and are supported by detailed record-keeping.

At The Morton Arboretum, there are nearly 200 trees in the oak collection that represent species from around the world. Why would an arboretum curate an oak collection? Oaks are culturally, economically, and ecologically important trees, and they need conservation help.

There are approximately 450 species of oaks in the world. They can be found across the Americas, Asia, and Europe. Oak trees are majestic beauties and symbols of strength in many cultures. The oak is the national tree of not only the United States, but of England and Germany as well.

Arboreta use their collections as a laboratory for scientific research.
Scientists at arboreta are studying tree diversity.
Diversity, among and within species, is critical to the survival of trees. A diverse collection of trees is more likely to survive environmental stresses. With more research and new technologies, scientists can document the rich biodiversity of the world and understand what we may be losing. The chart to the right illustrates how a DNA analysis of paper-barked maple (Acer griseum) samples confirms the lack of genetic diversity in the species’ population.This type of research informs efforts to increase biodiversity in urban areas and maintain healthy plant communities in the wild.

DNA can be extracted from herbarium or living specimens and used to answer important questions about biodiversity and the evolution of form and function in trees.
Analyzing DNA can help arboreta with plant breeding and improvement, population management policies, and conservation decisions.

Genetic techniques have been used to improve conservation efforts for the paper-barked maple (Acer griseum). This tree is endangered in the wild in China because its populations have been fragmented and often produce seeds that cannot grow.

Working with scientists from all over the world, researchers from The Morton Arboretum collected samples to assess the genetic diversity in paper-barked maple trees that live in arboreta and gardens, as well as in the wild. Scientists can use this information to identify populations of paper-barked maple that harbor the most genetic diversity.

Arboreta also study trees and forest health.
Arboreta invest in the health of trees. Because they are part of an ecosystem, trees can be dangerous when trunks, roots, or branches fail. Specialized researchers study why and how trees fail. Their findings can improve how we manage trees in collections, urban environments, and the wild.

Root biology is a key area of tree science. Roots are important for the health and stability of trees: they take in water and they anchor the tree to the ground.

Since roots can grow 18 inches per year in the midwest climate, trees have to be planted in areas that can accommodate their root structure. Restricted urban environments can be detrimental for the health of trees. By studying roots, arboreta can help cities more effectively choose and maintain trees.

Roots are underground, so learning their secrets can be difficult. New technology lets scientists see roots in new ways.

Researchers at The Morton Arboretum learn about root structure and how roots grow by developing 3D models to study these intricate systems.

Arboreta develop new types of pest- and disease-resistant trees.
Pests and diseases can devastate entire tree populations. In response, arboretum researchers study, select, and breed trees that can resist these threats.

George Ware (1924-2010) was hired at The Morton Arboretum in 1968; his research focused on urban tree breeding and improvement. At this time Dutch elm disease, caused by a fungus from Asia, was devastating the most commonly planted street tree in American cities. Ware saw the potential in Asian elms and began hybridizing and breeding trees that were resistant to Dutch elm disease and could thrive in urban conditions.

The Morton Arboretum introduced Ware’s cultivar ACCOLADE® elm (Ulmus davidiana var. japonica 'Morton') to the world. This beautiful tree, which is an Asian hybrid, demonstrates good resistance to Dutch elm disease, elm yellows, and elm leaf beetle.

The Morton Arboretum continues to breed new species that will succeed despite urban challenges like compacted soil, pollution, and restricted growing sites. The Arboretum partners with the Chicago Botanic Gardens and the Ornamental Growers Association of Northern Illinois in the Chicagoland Grows® Plant Introduction Program to bring to market new trees and shrubs that thrive in difficult local environments.

Arboreta help cities and communities.
Urban environments can cause challenges for tree growth. Arboreta share their latest research through outreach and education so cities, neighborhoods, and homeowners can choose varieties that will survive and provide benefits for their ecosystems.
Arboreta collaborate on a global scale.
Arboreta help conserve tree species by collaborating with gardens worldwide through collecting trips and joint initiatives. Not only do arboreta share seeds and living specimens, they also share research, knowledge, and skills. For example, The Morton Arboretum is a founding member of the North America China Plant Exploration Consortium. Arboretum staff members have participated in collecting trips to China for over 20 years.

Formal partnerships around the world strengthen tree conservation efforts in gardens and in the wild, assess genetic diversity of threatened tree species, and develop programs that support tree conservation education.

For example, The Morton Arboretum is a champion of oaks, and collaborates worldwide to save this genus.

Some arboreta have joined together to collaborate and network via ArbNet, an arboretum accreditation program. ArbNet was developed by The Morton Arboretum to establish and share a widely recognized set of industry standards to unify the arboretum community, provide benchmarking, and share guidelines for professional development.

The ArbNet accreditation program recognizes arboreta at various levels of development, capacity, and professionalism. Registered institutions range from small, local cemeteries to large, established public gardens—all working to advance the planting and conservation of trees.

Be a partner in protecting trees and forests for future generations.
When you visit an arboretum, you can enjoy trees; learn how to identify, select, and care for them; and support ongoing research. 
Credits: All media
The story featured may in some cases have been created by an independent third party and may not always represent the views of the institutions, listed below, who have supplied the content.
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