City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: https://read.dmtmag.com/i/744699
32 City Trees Outside Their Comfort Zones Nearly ten years ago, the University of Missouri, where I worked as campus arborist, decided to increase the conifer collection at the Mizzou Botanic Garden. A number of unusu- al species were brought in and planted in various locations around campus. My initial thought was that many of these species, especially the western species, would not be too happy growing in heavy midwestern clay soils. As it turned out, that was the case as one by one, each of them died. Campus soils are not only very heavy and slow draining, but are also very compacted due to heavy foot traffic. A second round of conifers was purchased to replace the first lot. This time I decided to change tactics and plant higher. All of these trees were B&B stock and some had 44-inch (112 cm) balls and were very tall because of this. The plan was to dig a shallower planting hole and shave off some of the lower root ball where roots were barely present. I then mixed up 1/3 topsoil, 1/3 sand, and 1/3 pea gravel. This mixture was mounded up to the root ball and the trees were staked. These trees received extra watering the first season or two as do all new plantings and then were on their own. Unfortunately, city foresters must avoid using hemlocks like this weeping variety (Tsuga canadensis 'Pendula') in areas with hemlock woolly adelgid infestations. Photo by Michelle Sutton In Nashville, using conifers in the urban environment has gone in and out of style. Most recently, arborvitaes (Thuja) have been used as an evergreen screen; however, after snow their branches tend to flop over from the weight. If they do not correct themselves, we will cable them. Yews (Taxus) continue to do well here though are mostly used as a foundation shrub. Often when cypress (Cupressus), pines (Pinus), or cryptomerias (Cryptomeria) are used, they may grow well for years and then in a drought will quickly die. (An old local saying is, "There are no native pines in Nashville.") Also, the availability of conifers is a consideration. On aver- age, Nashville's climate tends to be a little too hot for coni- fers which has reduced the demand and therefore, the area nurseries tend not to stock them. —Jennifer Pine Smith, Horticulturist, Metro Landscape Coordination Program, Metro Nashville Public Works