Tree program nurtures St. Paul’s urban forest, and young people learning arborist skills

While walking her dog earlier this year, Raegan Carpenter pondered career options. The 24-year-old had done some landscaping and thought she might enjoy work that involved trees. When she got home, she googled "arborist training" and found a result for a program at Tree Trust, a St. Paul nonprofit organization.

Fast forward to a recent cool late-October morning, which found her planting a linden tree along Furness Parkway on St. Paul's East Side. Carpenter trimmed off the excess roots that grew in the tree's nursery container and peeled away layers of dirt to find the root flare — the area where the tree's main roots connect to the trunk. A crew member dug a hole with a large auger, and she buried the roots in the ground, carefully adding water and stomping down excess soil with Tree Trust senior trainer Emily Cleaver.

Tree Trust has a contract with the city of St. Paul to plant new species aimed at replacing the thousands of ash trees lost to emerald ash borer, an invasive beetle that has destroyed ash across the Midwest. The nonprofit planted 715 trees in the spring and 850 more this fall.

"For a lot of them, it's figuring out if they like it or not," said Keegan McKye, a senior trainer with Tree Trust.

Job prospects are good, Cleaver said, with cities across Minnesota and the Upper Midwest dealing with the ravages of emerald ash borer . State and local governments are removing tens of thousands of doomed or infected ash trees and replacing them when possible. The beetle will ultimately spread to all ash trees, experts say, and even chemical treatments that stave it off need to be reapplied every few years. There were an estimated 1 billion ash trees in Minnesota when emerald ash borer was discovered in the state in 2009.

Over MEA weekend, Tree Trust worked with a group of 37 high school students to plant 250 trees along Shepard Road on St. Paul's riverfront. The event allowed Carpenter to plant trees in her neighborhood, which was a bonus.

"These trees are going to get big, and they're going to be a significant part of the urban landscape for the decades to come, and these kids are going to be able to say they were a part of it," said Karen Zumach, Tree Trust's director of community forestry.

Emerald ash borer is just one of the invasive species destroying forests across the globe at a time when trees are desperately needed. Trees absorb carbon dioxide and clean the air, and are critical to combating climate change caused by the burning of fossil fuels.

Invasive species, disease and deforestation are pushing Earth's trees to the brink. A new study by the International Union for Conservation of Nature found that one-third of more than 47,000 examined tree species are at risk of extinction .

To mitigate the harm of future disease, foresters in Minnesota try to plant a diverse array of species when replacing lost ash trees. The crew working Furness Parkway had about 20 varieties, Cleaver said, including linden trees, honey locusts, triumph elms, eastern larches and London plane trees.

As Carpenter and Cleaver finished planting the linden boulevard tree, they poured a 5-gallon bucket of water over the soil, which the tree quickly absorbed. They put mulch around the tree to protect the roots and prevent accidental maiming by mowing crews.

Planting trees in the fall has advantages, Zumach said. The cold gives the trees a chance to adapt to their new home as they slow down for the winter.

"The trees we're planting now are already in coma form, and they're just going to be waking up in a new place," she said.