If a magician can rest comfortably on a bed of nails, why couldn’t a tree?
That may sound like nonsense, but it just happened in both principle and practice at the corner of Pattee and Pine streets. On Thursday, excavators dug a special hole in the middle of downtown Missoula’s future Art Park and buried a grid of 60 three-foot-tall black tubes. The dirt between the tubes will provide a fertile root bed for a Pacific sunset maple tree. The tubes themselves, like the bed of nails, will support a concrete patio strong enough to hold up a fire truck without compacting the roots below.
“See those honey locusts?” Karen Sippy asked, pointing to some 20-foot-tall street trees next to the Missoula Art Museum. “They should be 50 feet tall. But they’re growing in holes this big.”
Sippy held her hands together, barely framing her face. She's the director of the volunteer group Trees for Missoula, which helped raise more than $12,000 for the underground supports. Instead of a narrow hole surrounded by compacted gravel, that coming maple will have more than 900 cubic feet of loose soil in which to grow.
“This is my third installation this week," said Pat Greeley of DeepRoot Green Infrastructure, the company that makes the SilvaCell tubes. “These are going in Seattle, the Bay Area, Boise, Des Moines; Lincoln, Nebraska, even in Texas.”
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The tubes and their bases look like oversize versions of the disposable planters found at garden nurseries. They feel almost as flimsy. But placed properly and supported by loose soil, the tubes can distribute the weight of thousands of pounds of sidewalk, pedestrians, vehicles and activity.
The tree itself will go in a separate hole tucked into the corner of the L-shaped SilvaCell network. Greeley explained that trees don’t need symmetrical growing space – their roots will seek out any source of water and nutrients. That’s why boulevard trees often tunnel under (and buckle) sidewalks to partake of the more generous watering and fertilizing residents put on their lawns. Greeley said street trees that grow healthier than their neighbors often have tapped into a distant pocket of “heritage soil” left undisturbed by urban paving and development.
When finished, the $900,000 Art Park will fill the former intersection with landscaped grounds, changing sculpture exhibits and other public activities. A consortium of local businesses, private donors, Adventure Cycling, the city of Missoula, Montana Department of Commerce and Department of Natural Resources and Conservation all provided parts of the budget. It should be finished in early November.
Meanwhile, city arborists and volunteers have been scrambling to finish other tree projects before fall weather gets too cold. On Thursday afternoon, students from the University of Montana College of Forestry and Conservation transplanted about 55 new oak, crabapple, sycamore and maple trees from their nursery home at the Wastewater Treatment Plant to new homes at Wapikiya and Whitaker parks. More new trees have been placed along Third Street West, Playfair Park and Russell Park West.