With snow blowing sideways Tuesday morning, Pittsburgh Parks Conservancy horticulturists Jaci Bruschi and Angela Yuele and intern Emily Cumpston set about planting 100 yellowwood saplings along a hillside in Schenley Park off Frew Street.
Now dormant, these tiny specimens will become a living laboratory in the spring as the pilot species in the Schenley Park Tree Research Grove.
The American yellowwood is an enigmatic species to be testing out in this climate zone. It isn’t common this far north, but there are about 10 known specimens that are mature and healthy right in Oakland, including Schenley Park, said Phil Gruszka, the conservancy’s director of horticulture and forestry.
They are proof the yellowwood could flourish here, because within the genetic makeup of the species, some specimens leaf out later and have withstood northern weather, he said.
A member of the pea family, with drooping, fragrant white blossoms and yellow autumn foliage, the yellowwood is most common in southern tier states, from Oklahoma to North Carolina. Its occurrence in northern states may indicate the species once had a wider range and that the fittest survived conditions that pushed the others out.
“If we can identify the genotypes that do well here, with global warming they will be a better species growing here in 100 years,” he said.
Among these 100 saplings, the number that show the most resilient qualities will be chosen for continued research as they grow. The others will be transplanted throughout the park system, he said.
Study tree growth in Schenley Park “In the spring, we will record when they break bud, and as they grow we will be looking for form,” he said. “An upright growth habit will be more suitable near traffic, and a U-shaped crotch is better than a V-shape to withstand storm damage.
“We will sequence their genes to see how diverse they are. We’re hoping for five to 10 candidates to go forward with, but there could be 80. We don’t know yet.”
Yellowwoods that leaf out too early in northern states can develop a canker disease from being zapped too many years by late frosts. This disease has kept nurseries from growing them for sale in this region.
Mr. Gruszka said most nursery trees are propagated from cuttings, grafts or tissue culture to create certain qualities, which make them clones. These trees replace older trees that grew from seeds, but cloned trees have no heirs.
“These old trees from 100 years ago have genetic diversity and have been through all you can throw at them,” he said, opening his arms to frame a hulking oak across the way, its trunk encircled with root flares. “That old oak is screaming, ‘Bring it on!’ asking, ‘Why are you propagating?’”
Tree Pittsburgh collects the seeds of hardy trees that scream at us, growing them at the Heritage Nursery along the Allegheny River in Lawrenceville. It grew the 100 yellowwood saplings that are planted now at the Schenley Park Tree Research Grove.
The site has space for 600 trees for research, Mr. Gruszka said, adding, “We’re getting our feet wet with the yellowwood to make sure our protocols and our thinking are in order.”
The site will be informally named Fezziwig Grove for a character in Charles Dickens’ “A Christmas Carol,” at the request of the anonymous donor who gave the Conservancy the money to establish the research site.
Diana Nelson Jones: firstname.lastname@example.org or 412-263-1626. Twitter@dnelsonjones.