A Boulder professor's apple tree discovery sparked a local preservation movement

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After years spent mapping the remnants of Boulder County’s once-vibrant apple tree population, a local preservation project is now planting new orchards to help ensure rare and nearly forgotten varieties aren’t lost forever.

The Boulder Apple Tree Project (BAPT) began in 2017, when CU Boulder ecology professor Katie Suding’s children spotted an old apple tree growing improbably in an open prairie near their home. She pulled together a team of scientists, historians and community members to find out why an apple tree was growing there on Boulder’s open space.

“She just followed her curiosity,” said Amy Dunbar-Wallis, the project’s community coordinator. “How did that apple tree get here? What’s the story?”

The group launched its first “Apple Blitz” in 2018, documenting apple trees across Boulder County. What they found surprised them: Boulder and Colorado more broadly had been home to a thriving apple industry in the late 1800s and early 1900s.

“Apples travel really well and the history of apples is also the history of human migration,” Dunbar-Wallis said. “We have apples in the Eldorado Canyon area because of mining and because there were orchards there to supply the hotels that were just up the road from there.”

As Boulder grew, more orchards moved toward North Boulder, often near ditches. Aerial photos from the 1930s reveal where many once stood and where some remnant trees remain today. But as the apple industry decamped for Washington State and consolidated around a few varieties bred for durability over flavor, the U.S. apple catalog reached a genetic bottleneck, with thousands of varieties lost.

To identify apple varieties, BATP uses genetic testing, focusing on the oldest trees, which are more likely to be rare varieties and nearing the end of their roughly century-long lifespan.

Because apples don’t grow “true” from seed, the only way to preserve a variety is through grafting — a method that clones the original tree and keeps its lineage alive. DNA from unknown trees can be matched to a library of known types.

From 2018 to 2022, the team held community mapping blitzes, with data collection supported by students at the University of Northern Colorado, Front Range Community College, Red Rocks Community College and Fort Lewis College.

To date, they’ve located more than 1,000 trees across Colorado and northern New Mexico, identifying about 30 named cultivars and dozens of others through DNA testing.

In recent years, Dunbar-Wallis said the focus shifted from locating apple trees to protecting them.

“How do we preserve them and make sure that they don’t get lost for eternity?” she said. “That turned into, there’s a need for regional preservation orchards.”

In 2022, the City of Boulder reached out about a small parcel of land that had been cut off from a larger agricultural field decades ago when the Diagonal Highway was expanded. It had been taken over by prairie dogs, and the city was curious whether it could be used for an orchard. With help from the Bridge House ready-to-work program, the project cleared the land and planted about 30 trees in 2023. Now five to six feet tall, they may bear fruit this year.

That success sparked a second orchard — this one on the CU Boulder campus, near 30th Street. Students from the original project secured a grant from the CU Environmental Center and broke ground last fall, replacing sod with young trees, drought-tolerant blue gramma grass and native understory plants such as prairie grasses and wildflowers. The trees went in on May 3, but as two-year-old whips, they’re not much to look at just yet.

“We’re gonna have Macoun in there. We’re gonna have Wealthy, we’ve got Wolf Rivers going in and we’re gonna have some Black Twigs, just a really great mix of Colorado heritage-type apples,” Dunbar-Wallis said. “This isn’t going to be a fenced orchard, which I’m really excited about. So folks will be able to move through it pretty freely once the trees are more established.”

All fruit will go to the Buff Pantry, which helps to feed food-insecure students and staff. The orchard will also serve a variety of purposes for others around the university.

“We’re glad that it’s going to be an outdoor classroom available to all different majors at CU,” Dunbar-Wallis said. “We’re anticipating that the biology students can use it. Art students can use it. It’ll be a nice place of reflection.”

On the community side, volunteer opportunities will open at both sites once the trees are more established — a few years out, Dunbar-Wallis said. “We do anticipate folks helping with picking, pruning, gleaning, preparing the orchards for winter.”

In the meantime, the public can still take part in the annual April Grafting Day, which this year included CU’s farm and garden club and CSU agronomy students. The apple blitz pivoted in 2023 to fall orchard prep. And residents can continue reporting trees through a student-developed app.

“If folks have a tree that they want tagged and they see it hasn’t been tagged,” Dunbar-Wallis said, “they can download that app and they can geotag it and input all the information about that tree so that we have that for future use.”

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