This year Minneapolis residents have seen a large number of boulevard tree deaths due to disease, drought, and damage from construction and development projects. More than 6,000 trees have perished from Dutch elm disease alone. And while that number is considerably lower than last year, when nearly 10,000 city elms were lost to the highly contagious disease, concerns have been raised about the sustainability of our urban forest—especially the vast number of trees that occupy our boulevards.
Meanwhile, city departments are squabbling over who’s responsible for keeping those trees alive and residents may not even know what role they’re supposed to play.
“We’re slowing the rate of losses to Dutch elm disease, but it can’t be stopped—there is no cure,” said Ralph Sievert, the Park Board’s director of forestry, adding that for years the Park Board has been replanting with fewer elms to diversity its urban forest.
But replacing elm trees with other varieties can also be problematic, particularly when the trees are planted along boulevards. “Boulevards are traditionally the worst place to try to grow trees because there is a lot of buried debris in the soil,” explained Gary Johnson, professor of Urban and Community Forestry at the University of Minnesota. He said that city Public Works projects, such as sidewalk repair and road construction, can sever roots and invert the soil from its normal strata. In addition, smaller-than-normal root spaces, soil compaction from foot traffic, and exposure to de-icing salts contribute to a harsh environment for boulevard trees.
Ironically, American elms, the trees most susceptible to Dutch elm disease, can withstand boulevard conditions much better than other varieties. Johnson said that sugar maples do best in native rich-soiled forests. White and green ash trees thrive in lowland areas with plenty of moisture. Bur oak is a better choice for boulevard trees, but like many oak varieties, requires acidic soil and uniform moisture.
“These other trees don’t have near the credentials in boulevard sites [that elms have], and as a result, they’ll do fine for a few years and then we start having all these unexplained losses. Most of the time for these trees it’s layer upon layer of stress . . . and maybe poor planting techniques or poor stock,” said Johnson.
Consistent tree watering is critical to sustaining the city’s urban forest—especially for young trees—and ultimately it is a community responsibility. Sievert said that the Park Board, which oversees all of the city’s public trees, waters new trees during planting and then again about two weeks later. After that, watering public boulevard trees becomes the responsibility of the resident homeowner.
Sievert said boulevard trees planted near rental property or multi-unit dwellings are sometimes neglected because no one takes ownership. “It’s harder to get somebody to water a tree on a rental property than it is if somebody is a homeowner,” he said. “Sometimes if it’s a big apartment building where there are numerous residents, people think, ‘I’m just renting, so what do I care?’”
Who’s in Charge?
Although there is no formal, written agreement between the Park Board and the Minneapolis Fire Department (MFD), the MFD assists with watering trees during dry spells. Assistant Chief Ulie Seal explained that the captain at each of Minneapolis’s 19 fire stations delegates a watering schedule to his team. During normal weather conditions, the MFD does not water trees, but when there are extended dry periods, it lends a hand.
“This year in early spring it was dry, so we were out [watering],” said Seal. “Later in summer we had more rainfall so we cut back, then when it got dry again in August we were out. This time of year you have to be careful about watering too much because you don’t want to subject the trees to an early freeze.”
But the fire department can’t make watering trees a priority. “The reality of it is we do as much as we can, but our main function is to respond to fires and emergency situations,” said Seal. “Typically we get 90 to 100 calls per day; that’s more than 30,000 runs per year.”
Increasing tree stewardship in the community is part of the Park Board’s mission. Last year it created and appointed the Minneapolis Tree Advisory Commission (MTAC) to coordinate tree-related issues, explore and acquire funding and report annually to the Park Board and the City Council.
The 11-member MTAC includes Johnson and Sievert as well as representatives from the four corners of the city, arborists, and appointees of the City Council and mayor. The commission evolved from efforts between the Park Board and the City Council’s Urban Forest Policy group. In addition to tracking issues like disease and drought conditions, MTAC monitors damage to trees related to construction and development projects.
“There can be damage to existing trees through the construction of curbs and sidewalks,” said MTAC chair Peggy Booth. “If a tree’s roots are cut on one side of the road during curb construction and severed on the other side of the street during sidewalk construction, the tree becomes susceptible to wind throw and can fall down during a storm.”
MTAC also affects public policy that relates to trees. “The city’s sidewalks division of Public Works oversees repairs,” explained Sievert, noting that in the past the Park Board’s recommendation to curb sidewalks around trees was not always implemented by contractors. “Now it’s a requirement, a formula for contractors,” he said.
Sievert also noted that while trees are sometimes sacrificed for development, contractors are often required to fence off and work around large trees during construction. He said the City Council is currently working to develop a streamlined permitting process for developers called Minneapolis One Stop, and the Park Board is involved in the site plan review to ensure that adequate landscaping and greening components are part of developers’ agreements.
Despite factors like disease, drought, and damage, the Park Board estimates that more than 90 percent of the 2,400 trees it planted this year will survive.