Field Guide: Cowling Arboretum and McKnight Prairie

Cowling Arboretum

“Carleton’s location on the Cannon River [represents] a diversity of land contour . . . there are stream banks, sedge bogs . . . low grassy plains . . . bluffs of jutting rock . . . dry oak knolls, [and] fertile loam plateaus ideal for our mixed forests. It is doubtful whether any other educational institution in the Northwest has so admirable a site in such proximity.”
—Carleton botany professor Harvey Stork, who helped establish the Cowling Arboretum in the 1920s 

In the 1920s, two men who worked at a small liberal arts college in southeastern Minnesota had the foresight to designate a significant portion of their relatively new campus as an arboretum. Carleton College president Donald Cowling and botany professor Harvey Stork established the Arb, as it came to be called, and Stork and grounds superintendent D. Blake (“Stewsie”) Stewart were responsible for much of its early development. Their influences remain to this day. In particular, their planting of upland forest trees and wildflowers in the Upper Arb (Stork Forest) decades ago is now coming to impressive maturity.

Today, Carleton’s Cowling Arboretum and McKnight Prairie are open every day, year round. A 15-mile trail system laces the 800 acres of restored prairie and woodland. Hike or run in warm weather. Paddle a canoe or kayak down the Cannon River. Ski or snowshoe in winter. The Arb is a great place to unwind, watch birds, spot wildlife, and experience a slice of Minnesota as it appeared 200 years ago. You’re also likely to encounter students in classes ranging from biology and geology to English and art.



Guide to Flora and Fauna





monarch butterfly


red oak

pocket gopher




The waters, woodlands, and prairies of the Arb harbor at various times of the year more than 200 species of birds, 18 species of reptiles and amphibians, 37 species of mammals, and nearly 500 species of plants. You’re unlikely to see them all, but these examples are easy to spot.


Sharp-shinned hawks (top) fly at high speed through dense woods to surprise their prey, typically songbirds. Catch a glimpse of these speedy predators in Best Woods or in the floodplain forests along the Cannon River. 

Numerous bird species nest on the ground in the Arb’s prairie grasses. The eastern meadowlark (second from top), with a melodious trill and a black V on its otherwise yellow breast, is one of the more recognizable. 



Red oaks, identified by their multipointed leaves, are the most common tree in the Arb’s upland forests. Acorns are important food for blue jays, gray squirrels, and white-tailed deer. 

Minnesota’s native grasslands were called tallgrass for the dominance of species such as seven-foot-tall big bluestem (third from top)—sometimes called “turkey foot” because its seed head resembles the bird’s three-toed foot.



Several species of bumblebees (fourth from top) live in the Arb, pollinating many species of flowers as they forage for nectar. Wild pollinators and domesticated honeybees pollinate as much as 70 percent of the world’s flowering plants.

Monarch butterflies (fifth from top) sip nectar from various prairie plants, though their caterpillars eat only milkweed species (several of which are common in the Arb). Monarch populations have plummeted everywhere, partly because of the absence of milkweed on modern farms. 



The meadow vole, which looks like a dark chubby mouse, is perhaps the most common mammal in the Arb. Burrowing tunnels under the grass, voles are an important link in the food chain, preyed on by many carnivores, from weasels to owls.

The red fox (sixth from top) is a predator in the Arb. It weighs as much as a large cat and catches voles and rabbits.


Second Acts

During the late 1800s and most of the 1900s, the Arb uplands were plowed for corn and other crops. With the loss of native prairie and woodland, many native animals vanished as well. 

As Arb staff members, students, and volunteers have worked to restore the prairie through planting desired species, eradicating invasive ones, and using fire to reinvigorate select areas, several native wildlife species have reappeared. These include:

Minnesota’s once expansive oak savannas (seventh from top)—grasslands with widely scattered trees—have become scarce as trees have filled in to create dense woods. Arb managers have been restoring savannas here by cutting brush, removing nonnative buckthorn and honeysuckle, and burning beneath the mature oaks.

Pocket gophers (eighth from top) dig subterranean tunnels, creating telltale mounds of earth. They seldom emerge above ground because they find plenty to eat underground, including tree roots, grasses, and other plants. 

A large member of the weasel family, badgers (ninth from top) dig tunnels with their powerful front legs and claws. They eat other burrowing mammals, including pocket gophers, ground squirrels, and woodchucks.

The Henslow’s sparrow (tenth from top) is an inconspicuous and increasingly rare ground-nester that lives in large patches of dense grass, free from trees and other tall woody cover. Rather than fly, it prefers to run through the grass eating grasshoppers, beetles, and other insects. 

The red-headed woodpecker (bottom) finds its insect meals beneath the bark of old trees like other woodpeckers, but it also snatches flying insects from the air. One of many bird and mammal species that plan ahead, the red-headed woodpecker caches acorns and jams grasshoppers into cracks so they can’t escape. Its numbers have declined rangewide with the disappearance of open woods.


McKnight Prairie

McKnight Prairie is a never-disturbed fragment of original Minnesota prairie. Acquired in 1968 at the urging of biology professor Paul Jensen, McKnight is used today for faculty research and student projects. Located eight miles from campus near Stanton, McKnight has been an important source of seeds for restoring the Arboretum prairies.


Five Things Not to Miss

  1. Paddle the Cannon River: Paddling is easy and enjoyable on the quiet, winding Cannon. The stretch from just below the Second Street bridge in Northfield to the Waterford Iron Bridge in the Arb provides a lovely view of the Arb. The wooded bluffs create the illusion of a wilderness stream.
  2. Commune with the Chorus: As ice comes off Kettle Hole Marsh in March, mating western chorus frogs emerge by the thousands. These inch-long frogs sing in a rising tone that sounds like someone dragging a finger over the teeth of a comb. Wood frogs, which arrive even earlier when ice is still on the marsh, and northern leopard frogs, which arrive soon after, also may join the chorus. 
  3. Enjoy Spring Wildflowers: From mid-April through mid-May, trout lily, bloodroot, trillium, and large flowered bellwort carpet the floor of Best Woods and Stork Forest. But don’t procrastinate—these flowers bloom and then vanish quickly.
  4. Take the 15-Minute Escape: Just east of Bell Field and the tennis courts, a trail winds along the northern bank of Spring Creek, where the hardwood forest and burbling creek wrap you in a sense of quiet seclusion. The underlying Shakopee Formation dolomite is visible in outcrops along the trail.
  5. Hike to the Peak of the Prairie: Hiking north and east from campus in the Lower Arb, you’ll gradually emerge, surrounded by prairie grasses, at the highest point in the Arb. Sit on a large glacial erratic (a huge granite boulder transported by glaciers thousands of years ago) and look south for a commanding view of campus and Northfield.


Cowling Arboretum

Plan your Trip

Visit the Arb anytime. It’s open to the public year round.

• Keep dogs on a leash and pick up after them. 

• Ride your bike in the Upper Arb, but not in the Lower Arb. 

• Burn wood only in designated fire rings in the Upper Arb. 

• Don’t bring motorized vehicles or horses into the Arb. 

• Don’t camp or hunt. 


Additional Information

Download a trail map from the Arb website

A detailed interpretive guide to plant and animal communities in the Arb, as well as historic sites

Information about canoeing the Cannon River (and other streams), including up-to-date water-level reports

Information about McKnight Prairie, including directions from Northfield


Traces of the Past

Waterford Mill

Waterford Grange Mill 
Constructed in 1873 on the northwest bank of the Cannon River, this imposing mill ground wheat into flour and, beginning in 1895, generated electricity for Northfield and Waterford residents. The mill and dam ceased operation in 1905 and were destroyed in 1916, though mill foundations remain. Reach the site by hiking the trail on top of the old millpond dike.  


Waterford Iron Bridge

Waterford Iron Bridge
Once the bridge for Canada Avenue at the north end of the Arb, this iron bridge has been sidelined by a new highway crossing. It’s still open to pedestrian traffic and someday may be incorporated into a bike and walking trail. 


Druids Circle

Druids Circle 
Located just north of Spring Creek, the Druids Circle was built for the North American Reformed Druids, a group formed on campus in 1963 to protest Carleton’s mandatory chapel attendance. These days, the circle and table of stones are popular with students and visitors as a place of quiet reflection and study.


bridge plans

Old Suspension Bridge 
Concrete abutments on the east bank of the Cannon River, just north of campus, mark the site of a pair of suspension footbridges that crossed the river. The deteriorating bridges were removed in 1987.


Womens Club Cabin

Women’s League Cabin  
A simple cabin, constructed along Canada Avenue in 1938, served as a retreat for students who were Women’s League members. Used through the mid-1990s, the cabin had no running water and relied on a wood stove and fireplace for heat. Ultimately, college administrators decided the cabin was not worth the cost to refurbish it, and it was torn down in 1998.


Controlled Burn

For thousands of years, wildfires that were started randomly by lightning strikes or set intentionally by Native Americans swept across the hills that are now Carleton’s Arboretum. Wildfire suppressed the growth of trees, creating and maintaining grass-dominated prairies and open oak woods called savannas. Without fire, these grassy landscapes would turn eventually to thick woods.

Wildfires are rare these days, so Arb managers maintain the prairies and savannas with prescribed burns. The low-intensity fires kill invading trees and brush, consume dense thatch, and recycle nutrients. A given plot of prairie is burned on average once every four years.

Trained volunteers and student workers use drip torches to set the fire and water and hand tools to control and keep it in a desired area.

Arb burn


Four Seasons

Spring is the best time to watch birds in the Arb, as colorful migrating warbler species infiltrate the woodlands. Wild turkeys fan their tails in courtship displays. Spring ephemerals—briefly blooming wildflowers—explode throughout the forest.

By summer the Arb’s prairies are in full bloom. The tallest grasses reach more than head high. Barring heavy rains, summer is when to paddle the Cannon River and spot great blue herons prowling the riverbanks and painted, snapping, and spiny softshell turtles sunning on partially submerged logs.

Hit the trails in fall. The bugs are (mostly) gone and the hardwoods and prairie are turning to yellow, red, and russet. Prairie asters and goldenrods are in full bloom. At night, the rural sky is dark enough to show off the Milky Way and falling meteors.

Many trails are groomed for classic cross-country and skate-skiing. Snowshoeing is encouraged throughout the Arb. Search the snow for tunnels made by voles and tracks left by coyotes, foxes, raccoons, rabbits, and turkeys. 

tree overlooking Lyman Lakes


Volunteer Opportunities


European buckthorn, one of the most troublesome invasive plants in the Arb, was introduced by Harvey Stork in the 1930s, before we fully understood the damage nonnative species cause to ecosystems.

If you want to help restore a piece of Minnesota’s natural history, consider volunteering in the Arboretum. Volunteers remove invasive species, maintain trails, pick up trash, collect seeds, plant trees and shrubs, lead field trips, and monitor rare species. Specially trained volunteers also help with the prescribed burn program. Arboretum staff members host a regular work event from 9:00 a.m. to noon on the third Saturday of every month except December, January, and June. Learn more about volunteer opportunities.

Arbor is a program for current Carleton students who seek to learn more about the environment while helping to restore and manage the Arboretum and nearby McKnight Prairie. 

To learn more, visit: 
or contact: 
Nancy Braker ’81
Arboretum Director


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