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Issue link: https://read.dmtmag.com/i/744699
www.urban-forestry.com 27 Steel City Gymnosperms Conifers in the Pittsburgh area were targeted by the first settlers for one of the first industries of the Steel City, leather tanning. Hemlock (Tsuga canadensis) (Pennsylvania State Tree) and eastern white pine (Pinus strobus), which made up around 9% of the presettlement forest, quickly disappeared from the urbanizing landscape as the bark was used for the tanning pro- cess. Hemlock only returned to the city as an ornamental plant- ed in yards and cemeteries and in recent years has begun to disappear again due to the pressures of hemlock woolly adelgid and elongate scale. Eastern white pine has been planted where space allows—but no self-reproducing population of any conifer exists within the city. By far, the most common conifers in Pittsburgh are Colorado blue (Picea pungens) and Norway spruce (P. abies); the former is being devastated throughout the region by spruce decline. Austrian black pine (Pinus nigra), red pine (P. resinosa), and Scots pine (P. sylvestris) all seem to be on their way out as well due to broad swings in both precipitation and temperatures that favor fungal pathogens. A few years ago when we started a new campaign to plant 20,000 trees in Pittsburgh, we quickly realized that conifers were absent from many of our plantings. Aware of the local pest and disease pressures as well as rampant conifer theft from parks at Christmas time, we set out to find new species that would survive and thrive. Many local growers focus on the typi- cal spruces and pines that are sold as balled-and-burlapped or cut Christmas trees and that are overplanted and underperform- ing in the urban forest. We broadened our search and looked for specialty ornamental and conifer growers. Over the last eight years we have planted over 31 species and numerous cultivars and seedlings from the following 14 conifer genera: Calocedrus, Cedrus, Chamaecyparis, Cryptomeria, Juniperus, Larix, Metasequoia, Picea, Pinus, Pseudolarix, Sciadopitys, Taxodium, Thuja, and Tsuga. Top performers so far include Chamaecyparis nootkatensis and Metasequoia glyptostroboides, which includes the largest planted grove of Metasequoia in Pennsylvania. We found growers that didn't shear their trees, we purchased malformed specimens, and we secured weeping and other unusual forms all in an effort to avoid theft during the holiday season. To date, none of our newly planted conifers have been stolen. In 2012 the Pittsburgh Urban Forest Master Plan was released with strong diversity guidelines for tree planting that recommend that 20% of plantings (non-street) be composed of conifers. We have followed this recommendation in parks, cem- eteries, greenways, and medians—and the year-round beauty of conifers is now more noticeable in our public spaces. The Tree Pittsburgh Heritage Nursery, which grows 3-4 feet (.9-1.2 m) tall containerized seedlings for restoration projects Volunteers and Tree Pittsburgh Director of Urban Forestry Matt Erb (right) plant a Cedrus libani ssp. stenocoma in Pittsburgh's Arsenal Park. Several dozen of these hardy cedars of Lebanon have survived the last two polar vortices with little to no needle burn, while Leyland cypress (Cupressus x leylandii) in the area were wiped out. Photo Courtesy Tree Pittsburgh