The Largest Arboretums In The United States

Fall. That magical time of year when Mother Nature puts on her most dazzling displays of color. Fall can be enjoyed in countless places across the United States, and not just in the country's big forests. Arboretums, those public gardens built around living collections of trees and woody plants, are one of the best places to see this display. Here, trees are labeled and mapped, and many grow thousands of miles from their native habitats.

Arboretums come in all sizes, from modest city parks to sprawling forests covering thousands of acres. For this article, we've ranked America's biggest arboretums by the acreage each one currently publishes for its main grounds, counting only sites with "arboretum" in their official name. Satellite properties are left out, as are botanical gardens and nature reserves that don't carry the name. So, get out the leaf-peeping gear and check out the eight largest.

1. Bernheim Forest and Arboretum, Clermont, Kentucky

Located in Clermont, Kentucky, 25 miles south of Louisville, Bernheim Forest and Arboretum covers 16,140 acres, placing it firmly at the top of our list of America's biggest such parks. The land was bought and endowed in 1929 by a bourbon distiller Isaac W. Bernheim, and much of it had been logged out and mined for ore. The grounds seen today were designed in 1935 by the Olmsted Brothers, the firm run by the sons of Central Park designer Frederick Law Olmsted, and opened to the public in 1950.

Today, 600 acres serve as Kentucky's official arboretum, and the rest is beech and maple forest crisscrossed by more than 40 miles of trails. The Forest Giants, three huge figures built from reclaimed wood, are the most photographed stop, while the Canopy Tree Walk extends 75 feet above the forest floor. The site's fall festival, ColorFest, takes place November 7 and 8, 2026.

2. Holden Arboretum, Kirtland, Ohio

Ohio claims three of the top eight arboretums, starting with the Holden Arboretum in Kirtland, east of Cleveland. Holden pegs its size at 3,500 acres and was established in 1931 with money left by a mining executive. Most of the land is kept in a natural state, and two of its forests, Stebbins Gulch and Bole Woods, were designated National Natural Landmarks in 1967.

Highlights include the Murch Canopy Walk, a 500-foot elevated walkway suspended 65 feet above the forest floor, and the 12-story Kalberer Emergent Tower with its 360-degree view over the treetops.

3. The Dawes Arboretum, Newark, Ohio

The Dawes Arboretum, located just south of Newark, Ohio, covers nearly 2,000 acres and was founded in 1929 by a former congressman and his wife on farmland they had bought in 1918. By the time it was founded, they'd planted more than 50,000 trees on their former farmland. The grounds have grown from 293 acres since.

The best-known feature is the hedge lettering, which spells out "DAWES ARBORETUM" so that pilots flying overhead could read the name (the first hedges were planted in 1942). Volunteers replanted the whole thing in 1990 and 1991, and an observation tower near Dawes Lake gives the best view.

The 17-acre Japanese Garden, originally planted in 1963, has reopened after a two-year restoration. The arboretum's autumn event, Fall in Love with Dawes, takes place on October 24, 2026.

4. The Morton Arboretum, Lisle, Illinois

Located west of Chicago in Lisle, Illinois, the Morton Arboretum covers 1,700 acres and was founded in 1922 by Joy Morton of the Morton Salt family, whose father started Arbor Day, the annual tree-planting holiday. Laid out around the family's Thornhill estate as an outdoor museum of trees, it developed its early collections with help from Harvard's Arnold Arboretum.

Today, the living collections number more than 100,000 specimens representing 4,000 different kinds of plants, linked by 16 miles of hiking trails and nine miles of roads. Families head for the Children's Garden, and the Sterling Morton Library keeps a collection of botanical literature and art.

5. UW-Madison Arboretum, Madison, Wisconsin (Tied)

The UW-Madison Arboretum in Madison, Wisconsin, covers 1,200 acres and was inaugurated in 1934, after a group of university scientists persuaded the university and the city to let them restore worn-out farmland on the edge of town. The centerpiece is Curtis Prairie, where planting began in 1934 with help from 200 workers from the Civilian Conservation Corps, the Depression-era federal jobs program.

The arboretum has the oldest and most varied collection of restored ecological communities in the world, including tallgrass prairie, oak savanna, wetlands, and several forest types. It also has a lilac collection in the Longenecker Horticultural Gardens, and more than 17 miles of trails on land bordering Lake Wingra.

5. Minnesota Landscape Arboretum, Chaska, Minnesota (Tied)

Located in Chaska, southwest of Minneapolis, the Minnesota Landscape Arboretum is set on 1,200 acres, a far cry from the 160 acres it had when it began in 1958. That original parcel of land was bought with a gift raised by the women of the Lake Minnetonka Garden Club, close to a university fruit-breeding farm opened in 1907.

That farm is now the Horticultural Research Center, where the Honeycrisp apple was introduced in 1991. The word "landscape" in the name comes from the founders' aim of collecting trees with landscape value.

The Three-Mile Drive loops past most of the collections and can be driven or walked. The Oswald Visitor Center serves as the main entrance; newer additions include the Tashjian Bee and Pollinator Discovery Center, and the arboretum also runs maple sugaring programs.

7. Connecticut College Arboretum

The Connecticut College Arboretum in New London covers 750 acres and includes a working college campus. Established in 1931 on a 64-acre site with the Native Plant Collection, it now has 300 kinds of woody plants, a four-acre pond, the Laurel Walk, and an Outdoor Theater. The Caroline Black Garden, started in the late 1920s by the college's first botany department chair, is a three-acre garden of mature ornamental trees and shrubs.

The campus landscape counts as one of the collections and features more than 200 species of trees and views of the Thames River and Long Island Sound. Natural areas such as Mamacoke Island and the Bolleswood Tract make up much of the rest. The arboretum is open every day from sunrise to sunset with no admission charge.

8. Spring Grove Cemetery and Arboretum

Spring Grove Cemetery and Arboretum in Cincinnati, Ohio, is not only large, but also unusual. Covering 733 acres, it's the country's eighth-largest arboretum and its third-largest cemetery. The charter was granted for the cemetery in 1845, and 10 years later, the fenced family plots were replaced with open lawns and trees arranged around a series of connected lakes.

Its collection includes a national champion September elm, the largest of its kind in the country. Look for the Dexter Mausoleum, modeled after the Sainte-Chapelle in Paris, and the graves of Salmon P. Chase, the Chief Justice of the US Supreme Court who helped prepare the cemetery's charter, and of William Procter and James Gamble, founders of Procter & Gamble.

Where The Trees Grow

Fall is definitely the best time to visit an arboretum. Most of these properties are made up of forest, prairie, and wetland rather than formal gardens, which gives them a wide range of autumn color, from the beech and maple woods at Bernheim to the oak savanna in Madison. Several of them schedule their biggest events around the season, including ColorFest in Kentucky and Fall in Love with Dawes in Ohio.