OLYMPIC NATIONAL FOREST — Deep in the evergreen woodlands of Washington’s Olympic Peninsula sits a forest-within-a-forest: groves of Douglas fir, western hemlock, Sitka spruce and western white pine in evenly planted rows surrounded by a tall deer fence.

The Dennie Ahl Seed Orchard, the state’s largest at 123 acres, has grown here since the U.S. Forest Service established it in 1956. Its trees, selected for genetic diversity and sourced from areas with varying climates and elevations, were meant to produce a steady supply of seed to support replanting efforts after timber harvests.