Trees have been a landscaping priority for Yankton Parks & Recreation for more than thirty years. “Now the “Tree City USA” signs show it, entering the city along east Highway 50 and crossing the Missouri into Yankton on the Discovery Bridge. Lisa Kortan, Urban Forester for the City of Yankton, and South Dakota Department of Transportation made it happen.
“This will be the 31st year for Yankton meeting the criteria [of tree of tree planting and care].” She gives a nod to past city urban forester Stan Hoffart who established the effort.
Kortan’s tree projects this past season added more native trees and hardy cultivars as well as replaced some drought damaged trees. She comments on last season’s tree and associated native grass projects around Yankton.
Rotary Nature Park
Northwestern Public Service’s Huron office notified officials of Freeman, Mitchell, and Yankton that each were selected for $5,000 grants to purchase native trees, according to Kortan. “We’re re-designing plantings at Rotary Nature Park with native trees.”
Kortan aims for tree diversity. “We planted Quaking aspen, Burr oaks, Black Hills spruce, and a few more hackberries this fall,” she said. “Some hackberries are already along the trail.” Twenty-eight native trees were purchased locally and from area greenhouses.
“Northwest employees from the Yankton office helped plant the trees. They will be watered until the ground freezes,” she said. “These trees have about 1.5 inch diameter trunks. I’m not going to stake them this winter. I won’t stake them until next summer if needed. You want the root system to move a bit and stabilize the tree. In wet snow earlier, these trees leaned over, but when the snow melted, they popped back up.” She added that larger diameter trees or large trees planted with a tree spade or grown in a small container might need staking because the tree is top heavy before extra root growth.
The Auld-Brokaw Trail winds through Rotary Nature Park along Marne Creek. Established plants for the park need to have low water needs due to lack of a tap for irrigation water. A buffalo grass lawn has been growing for two years and 20 ft. x 8 ft. pods of wild flowers with fieldstone boundaries are planned for this park. “Possibly we’ll have labels on the wildflowers,” she said.
Access to stands of native grass and labeled perennials at Paddle Wheel Point and Rotary Park are short walks from the Yankton Area Visitor Center parking lot, she mentioned for plant enthusiasts.
“We lost seven arboretum trees in 2012,” Kortan said. “Now that we know the drought happened, it could happen again. I’ll be replacing them with hardy, drought-tolerant varieties. Stan Hoffart, the past city arborist, did a nice job establishing the arboretum. Because Yankton is borderline USDA Zone 4-5a, with the weather, some trees were under stress. We want to diversify what’s there as a learning site. Replacement trees for the arboretum included Matador Maple, Hot Wings Maple and Redleaf May Day Tree.”
Adjacent to the arboretum and south of Yankton High School, the arboretum trail winds through established bluestem and wildflowers. “This area has filled in well,” she said. It’s a kind of drainage bowl. Two years ago we burned the native grass and will again in winter. It helps get rid of the elm sprouts and thicken the grasses. Burning is better on the elm sprouts than using herbicide. Larry Nichols of the Yankton Fire Department and some volunteers help with that controlled burn before spring.”
Burn occurs while the grasses are still dormant, so they are unharmed. Elemental carbon from the burn nourishes the native grasses when they begin growing later in the season.
Trees and Drought of 2012
Severe drought of 2012 re-emphasized water needs of trees until they are established. Kortan aims to provide an inch of water per week for city trees less than five years old. Even with consistent watering, some tree loss was expected with city-managed trees during the drought that eased last season. “I was surprised that we didn’t lose more trees,” Kortan said.
“I noticed homeowners in town and surrounding area lost pine and blue spruce. Blue spruce isn’t a native tree like the Black Hills spruce. I removed about a dozen evergreens and continue to lose three or four larger elms. We planted more trees than we removed, and it was about the same as in past years. We did lose some five-seven year old maples. I think we may continue to see effects from the drought next season.”
She plans to continue the watering plan and is assisted by Kris Ford, a Yankton elementary teacher who works for the city in summer. Trees in parks, green areas such as near the granite fountain at Fourth St. and Broadway Ave. and diagonally across the avenue, and trees in medians on North Broadway are examples of trees that receive city care. Kortan continues a city tree inventory to better manage the trees.
Yankton Tree Inventory
Kotan recalls the weather events that destroyed trees last spring in Sioux Falls and early fall in Rapid City. She continues to inventory public space trees in the city of Yankton. “We record information about trees by age, height, variety, and location,” she said.
“We can apply for grants to help replace damaged trees if we have documentation. I use an aerial view of the city to help with a hand held GPS system to record the information.” Kortan, member of the SD Forestry Council in Pierre, had help from its committee to complete the inventory of park trees in Yankton and continues to work on right-of-way trees as possible. Now with the tree inventory, Kortan will have tree information at hand to maintain the tree city legacy.