By Published: Sept. 1, 2018


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. 

An unlucky run of crop-killing late spring frosts and disease outbreaks further sapped apple enthusiasm along the Front Range. The orchards dotting Boulder’s fields, hills and now-historic neighborhoods faded into the landscape. 

Today, a few hundred old apple trees remain in Boulder County, having long outlived their original caretakers. But many won’t survive much longer.

appleEnter 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.

apple illustration

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.

apple illustrationSuding 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.

apple illustration

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.”


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