(File Photo: Source for Photo: Joe Kostka searches for ripe pawpaws in his home orchard where he’s grown the native fruit for 21 years, in Natrona Heights, Pa,, Sept. 30, 2025. (Quinn Glabicki/Pittsburgh’s Public Source via AP)

(Allegheny County, PA) (AP) On a wooded hillside along the banks of the Allegheny River, Gabrielle Marsden brushed up against an oblong leaf: Asimina triloba. The American pawpaw.

The deciduous tree bears North America’s largest native fruit, and, as Marsden explained, supports the zebra swallowtail butterfly — a species that has all but disappeared from the Pittsburgh region.

“They don’t exist here, really,” Marsden said as she trekked along the river. The closest she’s found them is in Northern West Virginia.

“The most important thing for restoring any species is restoring their habitat,” she said, pausing below a grove of 40-foot-tall pawpaw trees tucked above the railway and flanked by the rusted frame of a Ford sedan. “Nature will do the rest.”

Marsden has become a foremost advocate for the preservation and local resurgence of the pawpaw and the butterfly that depends on it. She’s tied in with a growing community of enthusiasts and nonprofits committed to planting pawpaws and promoting the return of the zebra swallowtail.

Most butterflies have one particular plant that they’re drawn to. For the zebra swallowtail, it’s the pawpaw. Its larval caterpillar feasts on the tree’s long, obovate leaves.

At one point in time, millions of zebra swallowtails likely fluttered throughout the Pittsburgh region, explained Kevin Keegan, who studies moths and butterflies as the insect collection manager of the Carnegie Museum of Natural History.

But as Pittsburgh industrialized and riverbanks gave way to railways, steel mills and slag dumps, the zebra swallowtail disappeared. Keegan attributed as much as 95% of the species’ decline to industrialization. He estimated that as few as 100 zebra swallowtails remain in the Pittsburgh area.

Marsden has imported and released some, and others have reported a rare visit by a lone zebra swallowtail to home gardens with pawpaws.

“We can and we should bring it back,” Marsden said of the butterfly. Plus, she added, “pawpaw fruit is yummy.”

Looking out over the Allegheny River, Joe Kostka stood in his backyard orchard, surrounded by pawpaw trees. Green, fist-sized fruit littered the ground, and he roamed the grove, squeezing and sniffing, searching for ripeness.

“Look at this,” he said, gesturing overhead toward a fruit larger than a mango. “If that fell on your head, you’re gonna know it.”

Kostka and his wife, Diane, have grown pawpaws in their Natrona Heights orchard for 21 years. They’ve placed in the annual pawpaw festival in Ohio, one year taking third place for best pawpaw.

Their basement refrigerator is full of cultivars — pawpaws bred to be eaten, with fewer seeds and sweeter flesh. They’d collected about a dozen over the years — Shenandoah, Susquehanna and other varieties from the pawpaw research center at Kentucky State University and throughout the eastern United States.

After the pandemic, Marsden began hosting an annual party to raise awareness for the pawpaw and its ecological significance. Each time, she said, it’s grown in popularity, with nearly 200 people attending this year.

“I’ve been chasing pawpaws for four years,” said Adell Kitchens, a self-described forager and native plant-lover from McKees Rocks. “I’d never found one.”

The pawpaw can be elusive. The fruit has a relatively short season in late summer, and it’s not typically sold in grocery stores or farmers markets. “But it’s a local fruit, and it should be accessible,” Kitchens added. “These are like a unicorn,” Kitchens said after another bite of wild pawpaw, likening the flavor to a pear and avocado, crossed perhaps with a bit of banana.

Partygoers lined up for a smorgasbord of pawpaws both wild and cultivated, kombuchas, cheesecake, pawpaw ice cream and beer.

Beneath a tent, Jasen Bernthisel sat with the last of his pawpaw saplings. He’d already sold several hundred this year. “The pawpaw is really hot,” he said. A resilient, compact tree that bears fruit within a few years of planting, he explained, pawpaws make a lot of sense for home gardens and urban orchards.

“I feel like people are getting hip to them,” he said, looking around at scores of pawpaw partygoers. “This is evidence of it.”

Across town, at the site of a former steel mill in Upper Lawrenceville, Tree Pittsburgh has produced and distributed thousands of pawpaw trees since the nonprofit began growing native tree species 15 years ago.

What began as a small movement of niche interest in the pawpaw has grown substantially, and the organization has spent years hand-selecting a genetically diverse pool of pawpaw seeds, and sourcing others from across Northern Appalachia. Those pawpaws have been planted in public park restoration projects, along Pittsburgh’s many riverfronts and waterways, and in community orchards across the region. Hundreds have been adopted by locals through the organization’s tree adoption program.

“Demand far outweighs the supply,” said Megan Palomo, who oversees the organization’s nursery, which produces roughly 300 pawpaws a year.

After more than two decades growing pawpaw, the Kostkas finally spotted a single zebra swallowtail fluttering above their orchard last June. They found eggs laid atop a pawpaw leaf.

The newly certified members of the North American Pawpaw Growers Association carry seeds whenever they go hiking along the Allegheny, carving a shallow hole to plant them. They’re hoping more people will join the fruiting frenzy, and perhaps bring about a return of the elusive zebra swallowtail.

Keegan, the butterfly researcher, is cautiously hopeful: “Every little thing helps.”