City Trees

One way to achieve that greater diversity over time was by creating an in-house tree nursery. "That was critical because the range of trees avail- able in the trade then were so limited: mostly pin oaks (Quercus palustris), sweetgums (Liquidambar styraciflua), maples (Acer spp.), and lindens (Tilia spp.), all of which suffered downtown," O'Brien says. "One of the first species we grew on at the nursery was catalpa (Catalpa bignonioides) to plant around the parks. It is drought tolerant, and people and pollinators love its flowers! For the native catalpa sphinx moth (Ceratomia catalpa), catalpa foliage is its sole food source." O'Brien found that Kentucky coffeetree (Gymnocladus dioicus) is braced for whatever the Midwest throws at it. "Once the seedless Espresso variety became commercially avail- able, we planted it on streets and wherever we thought folks would have qualms with the pods," O'Brien says. "Coffeetree is drought tolerant, soils flexible, withstands the windy urban canyons … just super tough." One heroic coffeetree was planted in 1984 outside a popular downtown restaurant. The tree got run over by a car when it was young—but the crew quickly propped it back up, and it re-rooted. Then the restaurant behind it burned down in 2003, but the tree was only mildly singed, the building was rebuilt, and the coffeetree carried on (see left photo). O'Brien says, "The survivor coffeetree is still there, but not as big as we would like—that could be said of all downtown city trees—but one proactive thing we did was use a growth regulator to keep trees at a sustainable size so that they wouldn't spiral downwards due to limited rooting volume. That's an important piece of resilience; doing what you need to do to keep mature trees in place. Every year you're hanging on to a tree downtown is a year you're not replanting, with all the risk that comes with transplanting into a harsh environment." >> Located in northern Mid-Missouri, Columbia (pop. ~129,000) is a college- education-insurance town upland from the Missouri River Valley and just north of the northern border of the Ozarks. Mid- Missouri features prairies and forested hills and has a humid continental climate, characterized by four distinct seasons. It has a USDA Hardiness Zone of 6a, meaning trees and other plants need to be able to survive winter temperatures down to – 5° F (-20.6° C). Columbia averages 16.5 inches (42 cm) of snow per winter. Climate-driven events with lasting damage to Columbia's trees include the Missouri Flood of 1993 and the Missouri Drought of 2012. ucfsociety.org 27 Photo of Columbia College grounds courtesy of Columbia Convention and Visitors Bureau.

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