If the towering cottonwood that stood in front of Old Main could have talked, it would have had a lot to say about the last 140 years. 

It stood guard on commencement day. It was blanketed with heavy snow, endured windstorms and floods and basked in Boulder’s abundant sunshine. It witnessed romances, heated academic debates and gleeful Norlin Quad shenanigans.

In recent years, the iconic tree began to show its age. In January, crews gently dismantled its limbs and branches using a crane to remove the tree, which was dying off in large sections. As far as CU’s forestry experts can tell, it wasn’t affected by disease or injury — it simply got old.

“The metabolic functions of the tree start to become out of balance and the tree can no longer sustain parts of the canopy,” said campus forestry supervisor Vince Aquino.

Though the tree’s removal marks the end of a CU era, it also signifies new beginnings. In 2014, forestry staff took cuttings from the cottonwood and passed them on to colleagues in the EBIO teaching and research greenhouse, who rooted them in containers. With a little nurturing, the cuttings grew into small trees — exact clones of the Old Main cottonwood that Aquino and his team will plant near the original’s location.

“Everything in life is succession, something replacing something else,” said Tom Lemieux, the assistant greenhouse manager who helped propagate the tree.

The university spent $35 in 1879 to buy 42 plains cottonwoods, hardy trees that live up to 80 years. Few could have predicted the longevity and enormity of the Old Main cottonwood, which grew to 110 feet tall with a 19-foot base circumference. 

The Old Main cottonwood was the oldest, tallest tree on campus. On top of stellar genetics, the tree likely benefited from the campus’s historic flood irrigation system, and later a modern sprinkler system and forestry experts like Aquino and his team who cared for it. 

And the tree had regular visitors — many attending Aquino’s tree walks.

“Trees really elicit an emotional response in people,” said Aquino. “It can’t be overstated how much trees change what people feel when they’re in a landscape. It happens on a level that people aren’t even aware of.

[video:https://www.youtube.com/watch?v=CHMrbJZhsCM]

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Photo by Glenn Asakawa

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When the University of Colorado Boulder first opened in 1876, campus was nearly treeless. Today, it's home to approximately 5,000 trees and nearly 60 different species. Here, CU's Arborist Vince Aquino discusses the unique characteristics and attributes of trees, and why they are so important to the university's history.

See them for yourself with the CU’s Museum of Natural History’s self guided tree tour. 

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CU ecologists are tracking down the surviving trees of the Front Range’s all but vanished apple orchards — and priming a renewal.

On a high mesa overlooking Eldorado Canyon, an elderly apple tree stands alone. Its trunk is weathered, its branches bowed, but it is nevertheless resplendent with white springtime blooms. The tree is a hardy survivor, a witness to more than a century of Boulder history. 

As it nears the end of its life, CU researchers are trying to preserve its genetic legacy before it vanishes forever.

Apple trees are a largely overlooked element of Colorado’s agricultural heritage. In the late 1800s, pioneers brought seedlings from afar, planting orchards across the state that yielded varieties like the Maiden Blush, the Winesap and the Yellow Transparent. Near the turn of the 20th century, Colorado was one of the top apple-growing states in the nation, regularly exporting thousands of bushels by rail. An abundance of heirloom apple varieties, each with its own local quirks and flavors, offered Americans hundreds of unique varieties for eating, canning, baking and making hard cider.

By the 1920s, however, the newly invented Red Delicious gained popularity and Washington State emerged as the country’s new apple-growing hub. The commercial apple market shrank, with growers turning their focus to only the most profitable varieties.

All these trees have stories to tell. 

Enter CU ecology professor Katharine Suding.

She usually studies mountain ecosystems (and leads the university’s long-running Niwot Ridge alpine plant research project). But she was curious about the origins of the apple trees near her own Boulder County home and felt strongly that the trees represented natural and cultural history worth preserving.

Despite an estimated 7,500 types of apples worldwide and 2,500 in the United States alone, Americans’ apple consumption is dominated by just 15 common varieties, such as Red Delicious, Golden Delicious and Granny Smith. The selection at the grocery store barely scratches the surface of what once was — and again could be.  

“This effort could uncover rare and uncommon varieties that have been lost to time,” she said. “They probably represent a lot of diversity in our apple cultivars that we don’t have anywhere else today.”

Thus was born the Boulder Apple Tree Project. The first order of business was finding more of these historic trees.

Like old-fashioned sleuths, Suding and her students fanned out across Boulder to find and catalogue them. They consulted maps and journals, cross-referenced farming logs and scrutinized photos from the Norlin Library archives. Students hiked trails and canvassed neighborhoods block by block, an effort still underway

Whenever the apple hunters locate a tree (and obtain landowner permission), they mark its GPS coordinates and collect leaf and branch samples. The group has identified over 200 specimens so far, including in the Chautauqua area, the Mapleton neighborhood and one at the historic Doudy-DeBacker-Dunn home near the South Mesa trailhead — possibly one of the first apple trees ever planted in Boulder.

Along the way, the scientists have benefited from the wisdom of the crowd. Boulder residents eagerly chime in, reaching out with clues and tips and secret spots. Last spring, Suding and her colleagues created a free smartphone app for community members to submit tree info instantly. 

Back at the greenhouse on CU’s East Campus, Suding and her students extract DNA samples from the old trees in order to classify and compare them against a database of known varieties. So far, around half of the samples have returned matches. The other half may have no living equal anywhere in the world. 

These yet-to-be-identified trees are likely to be heirloom varieties worth reviving, either for ecological study or for commercial apple cultivation.

But apple trees have notoriously fickle genes: A tree grown from seed alone will not necessarily resemble its parent, making it difficult to conserve desired characteristics through traditional planting. Grafting, an age-old horticultural art that joins two plants together as one, could offer the solution. On greenhouse tables strewn with dirt and tape and pruning shears, Suding and team carefully attach wood from the old trees to a healthy root system. Then they place the combined stems into pots to be nurtured over several growing seasons.

Each successful graft will yield the genetic heir of a tree planted over a century ago, paving the way for these forgotten varieties to thrive again.

Suding isn’t the only person interested in a Front Range apple revival. In 2015, Eric Johnson (Edu’92) and Brant Clark co-founded the Widespread Malus project, an orchard in east Boulder that plants and manages grafted apple tree varieties from near and far.

“On one hand, we’re preserving old trees and repropagating them because we know they work here,” Johnson said, “and on the other, we’re gathering genes from wild apples because those are the tools that are going to make the apples of the future.”

Other citizen-led initiatives, such as the Montezuma Orchard Restoration Project, have in recent years compiled information about Colorado’s major fruit-growing regions. But the Front Range has remained largely uncatalogued until now.

The success of such an effort, Johnson says, will be built on the hard work of phone calls, door knocks and one-on-one community interactions like the ones Suding’s team prioritizes.

“I’m thrilled that they’re out there doing this,” Johnson said. “They have a lot of hands, they’ve mapped scores of trees already and they have really made a dent.”

The Boulder Apple Tree Project has the potential to answer important scientific and agricultural questions. The CU team also views it as an ongoing educational outreach effort, offering undergraduates the rare opportunity to participate in research efforts during their first years in college.

The simplicity of the project’s aim — saving lost apples — could serve as a crucial entry point to ecology for talented students, said ecology professor Lisa Corwin, a co-leader of the apple study: “Not all students believe research is for them, but if we can just get them out there, they may find that they love it.” 

For now, Boulder’s next generation of heirloom apple trees grows in a quiet corner of a CU greenhouse. The young, healthy stems, each about a foot tall, bear little resemblance to their gnarled forebears. Eventually, when the freshly-grafted trees are strong enough, Suding will plant them outdoors as a kind of “living laboratory” that will offer agricultural teaching resources for students and community members alike.

The revived apples might even pop up at local farmers markets someday, though they’re unlikely to disrupt the commercial dominance of the Red Delicious or the Granny Smith anytime soon. Still, they’ll offer Coloradans a taste of the agricultural diversity that once existed in their own backyard.

“The research is relevant and it’s tangible,” Suding said. “All these trees have stories to tell about the history of this place and the environment where we live.”

Comment? Email editor@colorado.edu.

Illustrations courtesy U.S. Department of Agriculture Pomological Watercolor Collection. Rare and Special Collections, National Agricultural Library

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When the University of Colorado Boulder first opened in 1876, campus was nearly treeless. Today, it's home to approximately 5,000 trees and nearly 60 different species. On May 22, Vince Aquino and Alan Nelson hosted their bi-yearly tree walk through campus to discuss the unique characteristics and attributes of trees, and why they are so important to the university's history. See them for yourself with the CU’s Museum of Natural History’s self guided tree tour. Below are a few of the trees you may spot on campus. 

Norway Maple

This maple is widely used in the U.S. as a shade tree. Classified as one of the hard maples, it grows moderately fast, is dust and pollution tolerant and disease and insect resistant. Its leaves are similar to those of the sugar maple but darker and thicker and have a milky juice. They appear earlier and last longer than those of our native maples.

Tartarian Maple

This small maple is native to Southeast Europe and Western Asia. It is close in form and overall appearance to the more common ginnala maple, but does not have ginnala’s consistent fall color.

Buckthorn

Buckthorn, one of the many names of this tree, is usually found in the Pacific Northwest growing from sea level to moderately high elevations. Buckthorn was first documented by the Lewis and Clark Expedition. Its bark was used by Native Americans to heal wounds and ailments. Its leaves are alternate and its black fruit is eaten by birds.

Redbud

The redbud is most commonly used as an ornamental tree because of its vivid lavender to pink blossoms that bloom in early spring before its leaves appear.

Red Maple

This maple, often planted for shade and its moderately rapid growth, is said to be the most prevalent tree in eastern North America. In the fall, this tree’s leaves will turn a beautiful scarlet or orange color. Its wood is used for furniture, crates or paper.

Baldcypress

A member of the redwood family, the baldcypress grows mainly in swampland, but can survive in other wet environments. It’s one of the very few deciduous conifers that drop all its needles in the fall.

Little Leaf Linden

This variety of Linden is a European native. Its heart-shaped leaves have unequal bases (the two sides of the leaf meet the stem at different places). This tree was moved with a tree spade about ten years ago, and it hasn’t grown very much since then.

Hemlock

Two different species of hemlock can be found in the western United States. The western hemlock (Tsuga heterophylla) is one of the four tree species that contribute the most timber. The mountain hemlock (Tsuga mertensiana) is one of the largest trees in alpine regions growing at elevations up to 11,000 feet. Hemlock groves in these areas are good shelter for bird nests and the tree’s seeds are a source of food for birds.

American Elm 

American elm was once very abundant in the United States. Due to the devastating effects of Dutch Elm Disease (a bark beetle borne fungus), this inverted vase-shaped tree has been significantly reduced in number. The CU campus used to contain about 1,000 American elm trees until Dutch Elm Disease ravaged the Boulder area. The campus now has fewer than 40 American elms remaining.

Hackberry

The Colorado native tree varies in size from short and shrubby to more than 100 feet tall. It has serrate (toothed) leaves and small, dark purple pitted fruit eaten by birds. Hackberry trees are susceptible to a mite parasite called a psyllid, which causes the formation of galls on its leaves.

Learn more about trees on campus here.

Information courtesy of CU's Museum of Natural History and Facilities Management; Top photo by Glenn Asakawa; Additional photos by Moe Clark

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CU Boulder’s main campus is home to thousands of trees. A conversation with lead arborist Vince Aquino.

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