The Pittsburgh Parks Conservancy's Horticulture and Forestry team is dedicated to creating a more resilient tree canopy. As part of this work, several years ago, the Parks Conservancy partnered with the City of Pittsburgh and the Penn State Cooperative Extension to plant Elm cultivars to understand elm breeding.

Did you know that American elm trees are the most susceptible of all to Dutch elm disease?

The Conservancy researched scientific and industry journals regarding the American Elm demise and all of the tree breeding work that was conducted to replace the American Elm in the urban forest. The City of Pittsburgh, Parks Conservancy, and Penn State Cooperative Extension identified a site in Schenley Park that could be utilized to further the understanding of elm breeding, planting cultivars from environmentally invasive parent species, and what that means to the urban forest.

The City of Pittsburgh's Forestry department removed the previously dying Norway maple trees from the identified area. The Conservancy and the Penn State Cooperative Extension partnered to plant elm cultivars readily available in the nursery trade. Before planting any elm cultivars, the Conservancy's Horticulture and Forestry staff surveyed the natural areas across the street from the planting, looking for non-native environmentally invasive elm species, such as Siberian and Chinese elms. None were determined to be present adjacent to the future planting site of the cultivar elms.

Cultivar

height x spread

parentage

Accolade

70' x 60'

U. japonica x U. wilsoniana

Prospector

40' x 30'

not hybrid, U. wilsoniana

Allee

50' x 35'

U. parvifolia

Triumph

55' x 45'

((U. japonica x U. wilsoniana ‘Morton’) x ((U. japonica x U. pumila ‘Morton Plainsman’)

Pioneer

50' x 50'

Ulmus glabra x carpinifolia

Frontier

40' x 30'

U. parvifolia x U. carpinifolia

Dynasty

40' x 40'

U. parvifolia - Korea

Valley Forge

 

U. Americana

New Horizon

60' x 50'

U. japonica x U. pumila

Vanguard

45' x 40'

U. japonica x U. pumila

                                                                               

The concern revealed in the review of journals centered around the lack of information regarding viable seeds. In tree breeding, most of the cultivars are generated by controlled crossing of pollen, which is getting one species to breed with another genetically similar species and genetically dissimilar ones.

Today, these elm cultivars attain the age where we anticipate seeing what the seed from these trees can become. The Horticulture and Forestry team studies the mulch rings around each cultivar and the hillside natural area for seedling germination. This study's outcome may not be revealed for years, but this team continues working to ensure that Pittsburgh's tree canopy remains resilient for decades to come.