Iowa State University’s campus functions as a living arboretum, with thousands of trees spread across roughly 500 acres of central grounds in Ames, Iowa. The entire campus has carried a formal designation as a botanic garden since the mid-1980s, making every walk between lecture halls a stroll through one of the most diverse tree collections in the upper Midwest. What sets this arboretum apart from a typical university quad lined with matching oaks is the sheer range of species, many of them deliberately planted over more than a century to serve both scientific and aesthetic purposes.
How the Campus Became an Arboretum
Iowa State’s relationship with trees dates to the university’s earliest years. Founded in 1858 as Iowa’s land-grant institution, the school attracted faculty and administrators who saw the open prairie landscape as a blank canvas. Early horticulture professors began planting specimen trees in the late nineteenth century, experimenting with species that could survive Iowa’s harsh winters and humid summers. By the early twentieth century, deliberate plantings had turned the campus into something much richer than typical institutional landscaping. Trees were chosen not just for shade or ornament but as teaching tools for forestry and horticulture students.
The formal recognition came in 1984, when the campus was designated a botanic garden. That designation reflected what had already been true for decades: the grounds held a curated, cataloged, and intentionally diverse collection of woody plants. The designation also created institutional momentum to maintain the collection, fund new plantings, and keep detailed records of what grows where. Today, the campus tree inventory includes hundreds of species and cultivars, from towering native oaks to unusual Asian conifers planted as experimental specimens generations ago.
Notable Species and Collections
A visitor walking from one end of campus to the other passes through what amounts to a compressed survey of temperate tree diversity. Oaks are among the most prominent residents. Bur oaks, with their thick corky bark and oversized acorns, are native to the Iowa prairie-forest border and thrive on campus. Red oaks and white oaks join them, along with less common species like swamp white oak and chinkapin oak, which were planted to showcase the breadth of the genus.
Maples are everywhere, from sugar maples whose fall color draws visitors each October to silver maples along stream corridors and ornamental Japanese maples tucked into sheltered courtyards. Conifers provide winter structure: eastern white pines, Colorado blue spruces, and several species of fir create green anchors when the deciduous canopy is bare. The collection also includes less expected finds like Kentucky coffeetree, ginkgo, and dawn redwood, a species once thought to be extinct until living specimens were discovered in China in the 1940s. Iowa State planted dawn redwoods on campus not long after seeds became available to Western botanists, and several of those trees have grown into impressive specimens.
Ornamental flowering trees punctuate the grounds in spring. Crabapples, redbuds, and dogwoods provide bursts of pink and white along walkways, while rows of honeylocust offer dappled shade in summer without the dense canopy that would block light from nearby buildings. The variety is deliberate. Planting a wide array of species reduces vulnerability to any single disease or pest, a lesson Iowa State learned the hard way.
Dutch Elm Disease and the Reshaping of the Canopy
For much of the twentieth century, American elms dominated the campus skyline. Their vase-shaped crowns formed cathedral-like arches over walkways, and they were among the most beloved features of the grounds. Then Dutch elm disease arrived. The fungal pathogen, spread by bark beetles, swept through the Midwest starting in the mid-twentieth century and devastated elm populations on campuses, city streets, and rural roadsides across the region.
Iowa State lost hundreds of mature elms over several decades. The loss was aesthetic and ecological: those elms had provided dense shade, habitat for birds, and a visual continuity that defined the campus character. Their removal left gaps in the canopy that took years to fill. The response reshaped how the university approached its tree collection. Rather than replacing elms with another single dominant species, grounds staff and horticulture faculty pushed for diversity. New plantings drew from dozens of genera, ensuring that no future epidemic could strip the campus bare the way Dutch elm disease had.
Some disease-resistant elm cultivars have since been planted on campus, including varieties bred to tolerate the fungus. These newer elms are not immune, but they can survive infection that would have killed their predecessors. They stand alongside the diversified plantings as a kind of hedge: a nod to the historic canopy without repeating the monoculture mistake.
The Emerald Ash Borer Threat
Ash trees represent another chapter in the ongoing tension between a beautiful campus canopy and the pests that threaten it. Green ash and white ash have been common on Midwestern campuses and city streets for decades, partly because they were planted as replacements after elm losses. When the emerald ash borer, an invasive beetle from East Asia, was first detected in Michigan in 2002, arborists across the region began planning for the worst. The beetle’s larvae feed under the bark of ash trees, disrupting the flow of water and nutrients and killing the tree within a few years.
Iowa confirmed the presence of emerald ash borer in the state in 2010, and the insect has since spread across much of Iowa. For a campus with a significant number of ash trees, this was unwelcome news. The university’s response has involved a combination of treatment and preemptive replacement. High-value specimen ash trees can be protected with insecticide treatments, but the cost and labor of treating every ash on a large campus are prohibitive. Many ash trees have been marked for eventual removal and replacement with species the beetle cannot attack.
The emerald ash borer situation echoes the Dutch elm disease experience in a disquieting way: a widely planted genus targeted by a single devastating pest. It has reinforced the campus philosophy of planting for maximum species diversity. Newer plantings tend to draw from genera that are not currently under major threat, including oaks, hickories, and less common species like yellowwood and hophornbeam.
Ecosystem Services of a Campus Forest
A campus arboretum is not just decorative. Trees on university grounds perform the same ecological work as trees anywhere: they absorb carbon dioxide, filter air pollutants, intercept rainfall, cool surrounding air through transpiration, and provide habitat for birds and insects. What makes a campus setting interesting is that these benefits are concentrated in a relatively small, heavily used area where thousands of people walk, study, and work every day.
Studies of comparable university campuses give a sense of scale. At Clemson University, for instance, researchers estimated that campus trees remove about 1.5 tons of air pollutants per year, including ozone, carbon monoxide, nitrogen dioxide, fine particulate matter, and sulfur dioxide. The same campus’s trees sequester roughly 77 tons of carbon annually and help reduce stormwater runoff by an estimated 99,200 cubic feet per year.1Land-Grant Press by Clemson Extension. Benefits of Urban Forests and Determining Their Value Iowa State’s campus, with a similar or larger tree canopy spread across a Midwestern climate that sees heavy spring rains, likely provides stormwater and air-quality benefits in the same general range.
Shade from mature trees also reduces cooling costs in nearby buildings. Large oaks and maples on the south and west sides of campus structures can measurably lower interior temperatures in summer, reducing air-conditioning loads. For a sprawling campus like Iowa State’s, where many buildings predate modern energy-efficiency standards, mature tree canopy is a form of passive infrastructure.
Walking Tours and the Educational Mission
Because the entire campus is a designated botanic garden, trees are labeled and mapped for educational use. Self-guided walking tours route visitors past notable specimens, and many trees carry identification tags listing their common name, scientific name, and sometimes their geographic origin. For horticulture and forestry students, the campus is essentially a living laboratory. Courses in dendrology, plant pathology, and landscape design use campus trees as teaching material, which means the collection is not just maintained for beauty but actively studied and referenced in coursework.
The educational value extends beyond enrolled students. Community members in Ames use the campus for recreation, and the tree collection draws garden enthusiasts, Master Gardener groups, and school field trips. Reiman Gardens, a public garden on the south edge of campus, adds to the botanical offerings with curated display gardens, but the broader campus canopy is arguably the larger and more varied collection. You can walk through groves of native prairie-edge species in one area and encounter unusual cultivars from East Asia or Southern Europe a few minutes later.
For anyone interested in trees adapted to USDA Hardiness Zone 5, where winter temperatures regularly drop below negative 20 degrees Fahrenheit, the campus is a practical reference guide. Every surviving tree on the grounds has proven it can handle Iowa’s climate, which makes the collection especially useful for homeowners and municipal foresters choosing species for the region.
Climate Adaptation and Future Plantings
Iowa’s climate is shifting. Average temperatures have risen, precipitation patterns have become more variable, and extreme weather events including derechos, ice storms, and prolonged droughts are straining urban and campus tree canopies across the state. The August 2020 derecho, a powerful straight-line windstorm that tore across central Iowa, damaged or destroyed trees across Ames and on the Iowa State campus. Mature trees with broad canopies and shallow root systems were especially vulnerable.
Storm damage and pest pressure have pushed campus foresters toward species that can handle a wider range of conditions. Trees with deep taproots, flexible wood, or tolerance for both wet and dry soils are favored in newer plantings. Bur oak, for instance, has deep roots and thick bark that make it resilient to wind, drought, and even low-intensity fire. It is a native species already well represented on campus, and it is likely to become more prominent as older, less resilient trees are replaced.
There is also growing interest in species whose native ranges lie slightly south of Iowa. As the climate warms, trees native to Missouri, Kentucky, or southern Illinois may find Iowa’s future conditions hospitable. Baldcypress, once considered too southern for reliable survival in central Iowa, has proven surprisingly hardy on campus and in nearby plantings around Ames. Sweetgum and tulip poplar are being tested in small numbers. The arboretum’s role as an experimental collection makes it a natural testing ground for these climate-adapted species, allowing campus foresters to observe long-term performance before recommending them for broader municipal use in the region.
Memorial Trees and Campus Landmarks
Some of the most photographed spots on campus owe their character to specific trees. The area around Lake LaVerne, a small artificial lake near the center of campus, is framed by mature willows, oaks, and ornamental plantings that create a park-like setting popular with students and visitors. The Campanile, Iowa State’s iconic bell tower, stands amid a landscape of mature shade trees whose canopy helps define the visual character of central campus.
Individual trees also carry personal and institutional significance. Memorial trees have been planted across campus for decades, marking the contributions of faculty, alumni, and community figures. Some of these memorial specimens are themselves unusual varieties chosen to stand out from the surrounding plantings, ensuring they serve as recognizable landmarks as well as living tributes. A few of the oldest trees on campus, particularly some of the bur oaks and white oaks, may predate the university itself, having established on the prairie before the first buildings went up in the 1860s.
These heritage trees occupy a special category in campus planning. They receive more intensive care, including structural pruning, lightning protection, and soil management to extend their lives. Losing a heritage tree to storm damage or disease is treated not just as an arboricultural event but as a loss to the campus community, and replacement plantings nearby are chosen with the understanding that the new tree will need a century or more to approach the stature of what it replaced.
How Iowa State’s Arboretum Compares to Formal Arboreta
A traditional arboretum is a dedicated facility where trees are planted in organized collections, often grouped by genus or geographic origin, with research and conservation as primary goals. Iowa State’s campus arboretum is something different: a working university campus where the tree collection is woven into the daily environment of classrooms, residence halls, parking lots, and athletic facilities. The trees share space with foot traffic, construction projects, utility corridors, and the general wear of a campus that serves tens of thousands of people.
This creates both advantages and constraints. The advantage is accessibility. You do not need to drive to a separate facility or pay admission to experience the collection. Every student and staff member interacts with it daily, which creates a level of community awareness and attachment that a remote arboretum might struggle to achieve. The constraint is that campus trees must coexist with infrastructure. Construction of new buildings sometimes requires removing mature trees, and underground utilities limit where new plantings can go. Balancing growth of the university with preservation of the tree collection is an ongoing negotiation.
The result is a collection that feels less curated than a formal arboretum but more alive. Trees grow in the context of a real landscape, exposed to real stresses, surrounded by people who may not even realize they are walking through a botanical collection. For anyone visiting Ames or passing through campus, the trees are worth noticing. Many of them have been standing longer than the buildings beside them, and with continued care and thoughtful replanting, many will still be growing long after those buildings are gone.