Environmental Science

Ashland has been accredited as a Level 1 Arboretum with 600+ trees and 44 species – a level of arboreal diversity not found in many places in the Bluegrass.

Ashland’s trees are not just beautiful, they play an important role environmental service by annually intercepting 520 pounds of air pollution, 24,920 pounds of carbon, and soaking up 202,296 gallons of storm water.

The inner Bluegrass is a beautiful landscape that is one of the most environmentally distinct in the eastern United States.  There is debate as to whether European settlers during migrations west in the 18th century encountered open savannas or densely wooded forests.  What is known is that trees living today, like the burr oak, blue ash, Ohio buckeye, and sugar maple have sprawled over the Bluegrass for hundreds of years. 

Ashland is nestled in the center of the Inner Bluegrass, within the city of Lexington, and it retains a variety of native tree species that are rare to find in an urban environment.  Over forty species are represented in Ashland’s over 600 trees.  The estate is an accredited Level I arboretum and home to multiple noteworthy trees: two blue ash trees that are nearly 300 years old, a Kentucky Big Tree Champion tulip poplar, a Kentucky Big Tree champion paper birch, the current Kentucky State Champion Washington hawthorne, living fossil ginkgo trees.

Henry Clay envisioned Ashland as a park-like environment where a variety of trees could be enjoyed by his family and visitors. 

Clay first encountered European gardens on his trip to Belgium to negotiate an end to the War of 1812.  These gardens left such an impression on him that when he returned to Ashland, he embarked on a plan to design the finest “pleasure grounds” in the United States.  He was quick to highlight native tree species, but he also imported trees from the Appalachian Mountains, such as hemlock, and from further away, such as Norway spruce. 

When Clay would leave Ashland for Washington, D.C., he would leave strict instructions that not one single tree be cut on the grounds in his absence.  This passion for the natural world and desire to preserve it has continued for over 200 years at Ashland, and the property remains well known for its leafy landscape.

Here are just a few of the trees that can be seen at Ashland.

Blue ash
A tree that is particularly suited to the Bluegrass region, the large number of blue ash, white ash, and green ash trees on the property are the origin of Ashland’s name.  There are multiple blue ash trees on the estate that date from Henry Clay’s time.  Blue ash has a gelatinous substance in its bark that was used as a blue dye by European settlers.  In recent years the invasive Emerald Ash Borer (EAB) has decimated Kentucky’s ash tree population.  Blue ash is more resilient to the EAB than white or green ash, but it is still susceptible when stressed.  Ashland’s ash trees have been inoculated against the deadly pest.

White ash
White ash is the most common ash tree in Kentucky.  The wood is extremely strong and is often used in baseball bats and bowling lanes.  White ash has the most striking fall color of any Ash tree.  The Ash Bedroom contains a set of furniture made for Clay’s son James when the new mansion was built in 1856.  The elaborately carved pieces are made from either white or blue ash on Ashland’s grounds.

Green ash
Green ash naturally grows in moist bottomlands, but it is planted in many areas due to its ability to tolerate a variety of growing conditions.  Green ash grows from Canada to Florida and is extremely adaptable.  Though brittle when young, the mature wood is excellent for woodworking.

All three of the ash tree species found at Ashland are listed as “Critically Endangered” by the International Union for Conservation of Nature.  American ash trees went from “Thriving” to “Critically Endangered” in just 20 years, and the destruction from EAB is ongoing.

Burr oak
Along with blue ash, burr oaks are stately trees that characterize the landscape of the Inner Bluegrass.  Some burr oaks live for hundreds of years and sprawl over open pastures.  They are possibly an ancient remnant from drier conditions during the last Ice Age.

Black locust
This tree has the most durable wood of all North American trees.  Black locust timber has been used for fence posts, railroad ties, and can live for approximately 90 years.  This tree produces fragrant and beautiful white flowers in May.  The “Locust Walk” was one of Henry Clay’s favorite locations on the Ashland estate.

Kentucky coffeetree
At one time the Kentucky coffeetree was the designated state tree. It occurs throughout Kentucky but is most common in open woods in the Bluegrass. With its bold form, contorted branches, unique bark, and clusters of large pods, the Kentucky coffeetree is a popular ornamental tree.  European settlers used the seed pods from the tree as a coffee substitute.  But the tree is poisonous and cattle have died from drinking water that contained Kentucky coffeetree seeds.

Ohio buckeye
This tree’s seeds look very much like chestnuts, but the Ohio buckeye is toxic to humans, pets, and livestock.  European settlers to the Bluegrass used the hollowed-out trunks of the Ohio buckeye as cradles.

Sugar maple
This is an extremely versatile tree that was highly prized by Native Americans and European settlers.  The sap can be used to make sweetener and syrup, and the timber is valued for its strength and beauty.  Sugar maple timber is used in furniture, flooring, gunstocks, bowling pins, and musical instruments.


This tree produces the largest fruit native to North America.  The pawpaw fruit has a tropical flavor, mixing characteristics of mango and banana.  Pawpaw fruit ripens in early fall, and the tree has no serious predators. 

From the genus Ginkgoales, which dates back 290 million years, ginkgo biloba trees have left evidence of their existence in fossils dating back 170 million years.  Ginkgo trees are considered a living fossil having changed very little genetically over their long existence.  Ginkgos were once common all over the northern hemisphere but their wild range decreased to a small area in China.  When American and European horticulturalists discovered the ginkgo tree, they quickly became a popular decorative tree.  The ginkgo trees located in front of the Ashland mansion are over 150 years old and were planted by the family.  While 150 years old might sound like a long life, Ginkgo trees have been known to live 2,500 years and survive nuclear explosions.

Bison regularly ate and distributed this native grass.  Once the bison disappeared from the eastern U.S., so did the Running Buffalo Clover.  Long believed to be extinct, Running Buffalo Clover was rediscovered in West Virginia in 1983.  Through reintroduction efforts the species is now thriving, including on the Ashland grounds.

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