National Park Service crews are rebuilding the 40 groves at Flight 93 National Memorial that define the field where United Airlines Flight 93 came down near Shanksville in Somerset County, Pennsylvania, with nearly 700 dead or declining trees out of the ground since April 2024. Today marks 25 years since the world changed, and the Park Service declared phase one of its Resiliency Project complete in December 2024.
“The trees are just not thriving the way we want,” Donna Gibson said, with the Friends of Flight 93 executive director raising US$1 million. She said it to volunteers in April 2024, and the Friends have since set the pledge at $100,000 a year for a decade. Superintendent Stephen M. Clark launched the project on 16 April 2024 with “the coalition of the tree and soil experts”, and the removals began that month.
Each grove holds 40 trees, one for each passenger and crew member, in a crescent along the entrance road. Nelson Byrd Woltz and Paul Murdoch Architects drew the 30-acre feature to define the Field of Honor, once an open-pit coal mine. The original trees were planted between 2012 and 2016, with sugar maple and white oak among a palette the designers list as seven species.
Cornell University’s team counted 76 dead trees among the 1,600 in the groves in a 2020 conditions assessment, and another 175 missing outright. It rated a further 276 in fair or poor condition, and the Park Service blames poor soils, drainage, and low-quality nursery stock.
Fifty years of coal mining left the 2,200-acre site with a few inches of soil and treatment ponds at remediation. Paul Josey, who managed the memorial for landscape architects Nelson Byrd Woltz, says the designers’ call to truck in topsoil was scrapped for budget reasons. Crews ripped the ground to decompact it instead, and Josey says the ripping reached only the first of two planting phases.
“There’s a real correlation with the phasing, where we’re completely replacing most of the groves that were planted during the second phase,” Robert Page said. The director of the Olmsted Center for Landscape Preservation is working with Cornell, Penn State’s urban forestry program, and SUNY-ESF on the plan.
Acting deputy superintendent Kristina M. Melgar and James Mealey presented a $6 million, 10-year plan at the memorial on 17 December 2024. Mealey, the Olmsted Center landscape architect on the works, had crews cut 225-foot corridors through groves 35 to 39 by then. Cornell’s team recommended the “scoop and dump” method: two feet of new topsoil and mulch at each planting site to improve drainage and root space.
The five groves would be replanted the following spring, Mealey said in December 2024, and by March 2025 that had slipped a year. The Park Service replanted grove 40 as a demonstration in 2022 with amended soil and a new mix of species.
Swamp white oak and Kentucky coffeetree performed strongly in a test grove, Mealey said, and may be included in the replanting. The 400 trees around the pools in Manhattan are swamp white oak, and the designers’ original arc carried only a few, with no Kentucky coffeetree.
Across the rest of the 2,200-acre memorial, the same reclaimed mine gave rise to a forest of 150,000 trees. Since 2012, more than 4,200 volunteers planted 41 varieties of native trees and shrubs across 197 acres.
The Park Service closed Plant a Tree at Flight 93 in April 2022, planning 14,000 seedlings over 20 acres for the finale. More than 160 businesses, service clubs, and academic and government bodies helped over the decade. The plantings “accomplished the largest concentration of American Chestnut trees in North America”, the Park Service states.
Pennsylvania’s Bureau of Forestry grew seedlings in Centre County, and Rosebud Mining came back to rip the compacted ground ahead of the 2018 planting. The American Chestnut Foundation and the Appalachian Regional Reforestation Initiative gave their services in kind.
Volunteers returned in April this year to work on the trees ahead of the anniversary, and rangers added more projects between then and September. Mealey told a public presentation in March 2025 that the partners were “not going to give up” on the groves. That timeline had the first replanting in groves 35 to 39 beginning this spring, and the Friends’ fundraising runs for a decade.
- For the timber that came out of Ground Zero itself, read Wood Central’s report on the gunboat now standing in Albany
