trophy tree
n. A large, fully mature, tree; such a tree that has been uprooted and planted in a yard or estate.
The landscaping rules now apply only to new commercial developments in designated areas. The rules require trees be planted in parking lots, along bare-walled building fronts and around detention ponds and trash bins.

Although the rules mostly require planting, they also protect large, healthy trees, called "trophy trees," and they created a "scenic corridor" designation under which residents of especially scenic roads may petition to have trees along the road protected.
—April Simun, “How trees are causing a tangle,” The State, January 17, 2002
When the house is a multimillion-dollar mansion, an instant tree isn't enough. Only a "trophy tree" — a giant specimen weighing up to 35,000 pounds —will do. "If they put up a new, 40- to 50,000-square-foot mansion, they want it to blend in," said Chet Halka Jr., whose Halka Nurseries in Millstone Township, N.J., charges up to $60,000 for a single mature tree: $20,000 for the tree and $40,000 to plant it. His customers have included singer Mariah Carey, boxer Mike Tyson, actor Eddie Murphy and Rolling Stone Keith Richards.
—Kim Palmer, “Instant trees,” Star Tribune, November 19, 1999
1991 (earliest)
The four-bedroom, three and a half-bath home includes about 3,900 square feet of living area and occupies a large lot (100 X 285 X 83 X 277) dotted with oaks — one of which is a trophy tree.
—Jerry Wallace, “'Hidden' new home surprises unveiled,” The Baton Rouge Sunday Advocate, January 06, 1991