Growing bigger trees that will flourish in a changing climate takes a long-game approach

For decades, tree-lined streets across the country — largely in the Southeast — would erupt in the bright white blossoms of Callery pear trees (Pyrus calleryana) every spring. Affordable, fast-growing and easily shipped, the trees had become the darlings of landscapers, municipalities and others, which also meant they were a favorite of those who could grow them — nurseries.

But in recent years, the Callery — known also by its most popular cultivar, the Bradford (P.c. ‘Bradford’) — has lost its luster. Its blossoms are pretty, but they stink to high heaven, drawing comparison to rotting fish and other smelly things. Their stems and branches sprout thorns — sometimes up to 3 inches long! — which have been known to puncture tires.

Native to Asia, the Callery is aggressively invasive, spreading into native forests, choking off other plants and snapping up vital resources for itself.

As a result, cities across the country started to quickly shift away from Callery pears, cutting them down and replacing them with less invasive and native species. Many cities have ordinances prohibiting the planting of Callery pears, and even whole states have taken action. South Carolina will implement a ban on new Bradford pear sales in October 2024, and starting this year, it is illegal to sell or plant any variety of Callery pear anywhere in Ohio.

The move away from Callery pears has been a good one for cities and fans of native trees. For nurseries that grow Callery pears, however, the hit has been a little harder. Some growers have found themselves with trees still in their fields that they are either selling at a loss or not selling at all. They’ve scrambled to shift to other species, but it takes years to grow trees to a size that most municipalities are after.

“It went from being a nice tree to one you can’t plant anywhere,” said Tyler Kuenzi, general manager at Kuenzi Turf and Nursery in Salem, Oregon. “It was too quick of a change and too big of an area. The market has had to readjust and resize. We’re still dealing with excess inventory from that.”

The Callery pear episode is just one of the kinds of trials and tribulations that nurseries who grow larger trees face. There’s also the potential for pests and diseases, fluctuations in consumer demand, potentially over- or under-planting, ever-present labor shortages and more. But with the right planning, some diversification, maybe a dash of genetics and a commitment to the long game, successfully growing and selling the bigger trees that the market is demanding these days is entirely possible.

“We are always tracking what our sales are, what are customers are saying they want and readjusting our planting,” Kuenzi said. “There always ends up being a time lag, because we know these trees won’t come out of the ground for years. But as long as there is not a dramatic drop-off — like we had with the pears — most stuff ebbs and flows, which helps minimize the risk.”

Roots in the industry

Carlton Davidson has been in the tree business for more than two decades, first with Carlton Plants in Dayton, Oregon, for 20 years and for more than four years with Bailey Nurseries, which acquired Carlton Plants in 2018. He said the nursery specializes in trees that are desirable and suitable for a range of landscapes, including municipalities, golf courses, parks and residential homes.

The nursery self-propagates as much as possible by growing scores of acres of seedlings in layer beds, and grows bare root trees that are ready to sell in two, three and four years. Many of the trees sold go to other growers, who then plant the trees in fields or containers for a few more years to get them up to a larger size.

Bailey also has a container division, which in recent years has moved away from smaller sizes and toward a focus on 10- and 20-gallon containers to help simplify inventory.

“We are moving away from the smaller ones to help manage our product line for profitability,” Davidson said. “It also makes life simpler, and customers appreciate and understand that. I don’t think we’ve missed a beat in making that adjustment. The container tree market has been strong and continues to see a lot of demand.”

He said Bailey’s teams, including sales and marketing, breeding and a “new variety group,” are always working to single in on the best-quality trees that can resist pests and diseases.

The nursery also works with research universities, such as Oregon State University, in developing or refining new trees. One underway at present is a triploid (seedless) variety of the Norway maple, a popular tree that has been spreading invasively in the northeastern U.S. A seedless variety would help contain its spread.

At Kuenzi, the nursery grows bare root liners and all kinds of trees, from shade and flowering to fruit, nut and specimen. Kuenzi said the nursery grows many of its liners in fabric grow bags, which help increase plant health and reduce losses when the trees are transplanted. Shade and flowering trees are also grown in the bags, which also allows them to be dug up anytime throughout the year. And the nursery is starting to move some of its Japanese maples into grow bags as well.

Kuenzi said the nursery always tries to stay on top of what kinds of trees the market is seeking, even though that can be tough given the long growing cycles. He said Kuenzi is able to minimize some risk by transplanting from one size to the next. For example, if the nursery plants 5,000 seedlings of a certain variety in greenhouses, but then sees the market shifting, it may only plant 3,000 of them in the next size up.

Mixing it up

Offering a diversity of sizes as well as species is also key to growing trees successfully. At any given time, Kuenzi will have 50 to 75 different varieties of shade trees. The nursery has also been adding some conifers to its mix.

“We’re just adding more to continue to diversify,” Kuenzi said.

Diversity is big at Bailey, too. In addition to growing hundreds of cultivars, the nursery also has a number of different growing operations in Oregon — in Yamhill County, on Sauvie Island and in Sunnyside — as well as in Washington and Minnesota. These diverse growing locations help spread out risk and minimize losses versus planting everything in a single place.

Evolving with the times is key, too. Davidson said Bailey is constantly monitoring cultivars’ performance and refining as necessary. For example, when the Emerald ash borer started to become a threat, Bailey took action.

“Emerald ash borer was devastating,” he said. “It pretty much wiped out the ash market in the industry. We knew this would not be good for future sales, so we reduced our numbers and then eliminated that plant altogether. It’s no different than people having to change in their own lives like with their technology. What might have been good a decade ago may not be applicable anymore. You have to move forward.”

Similarly, Davidson points to the infamous ice storm of February 2021 and the devastation it wrought on the Willamette Valley’s stock of birch trees. The white-barked trees may be pleasing aesthetically, but their inability to survive an ice storm may not make them the best bet for a nursery’s future sales.
“Learning your lesson from what happens in the environment can help you decide which varieties to grow,” Davidson said.

Branching out

Part of Davidson’s perspective on tree selection comes from his work on the city of McMinnville’s landscape review committee. Part of that committee’s task is to try and ensure the city is planting the best possible tree varieties for today and tomorrow.

Nurseries often grow their trees with municipalities in mind and pay close attention to ordinances regarding variety, tree size and other factors. But Scott Altenhoff, manager of the Oregon Department of Forestry’s Urban and Community Forestry Program, thinks there’s more that could be done to help cities get the trees they want and nurseries to spread some of the risk in growing them.

“Why don’t we have better connections or established supply chains for municipalities?” he said. “It’s because, historically, municipalities and governments have not done the best job to work with nurseries to share risk. It’s all been on nurseries to see what the bestsellers are.”

Altenhoff said he first began looking into the issue after a symposium about 10 years ago focused on the role of trees in mitigating some of the effects of climate change.

He said there was a disconnect between growers, landscapers, urban foresters, cities and other stakeholders on everything from what kind of trees were most suitable to how to acquire them. What he’s been trying to do is foster communication and create at least an informal network for sharing information and resources.

Altenhoff pointed to a similar effort that’s happened in Chicago, where the city has been investing in the tree canopy, in part by entering into contract growing arrangements that include down payments to growers so they’re not having to bear all the risk. The Windy City has multiple tree-planting initiatives, including Our Roots Chicago and the Chicago Region Trees Initiative.

While the conversations are just in the early stages, Altenhoff said he’s confident that cities, nurseries, landscapers and others can work together to come up with an effective approach for growing, planting — and even paying for — the right kinds of trees across Oregon and, in turn, improving urban forests and tree canopies.

“The real challenge is promoting the understanding of how to get better trees everywhere they’re needed,” Altenhoff said. “Once that’s clear, we can make it happen. We just need to be strategic about where we are and where we want to be.”

From the April 2023 issue of Digger magazine | Download PDF