Sea-Tac 2025 Landscape Standards make native plants mandatory

Sea-Tac, one of the 10 busiest airports in the United States, just made native plants mandatory. 

That is not a small decision. That is 2,500 acres of future landscaping reclassified as ecological infrastructure.

Seattle-Tacoma International Airport's 2025 Landscape Standards — adopted by the Port of Seattle and effective for all new construction and renovation projects — require that native Pacific Northwest species constitute the primary plantings in all airport landscaping. 

The ferns, salal, red-twig dogwood, and native sedges visible in this photograph along the terminal drive are not a pilot project or a PR gesture. They are the new legal standard.

Sea-Tac handles 51 million passengers annually and operates in one of the most ecologically sensitive regions in North America — the Puget Sound lowlands, a temperate rainforest ecosystem that has lost 65% of its native vegetation cover to development since 1950. 

The airport sits in the middle of a landscape that historically supported Chinook salmon runs, western toad populations, and migratory shorebird habitat. The Duwamish River watershed — whose headwaters pass through the airport's drainage basin — is on the EPA Superfund list partly because of decades of contaminated stormwater runoff from impervious surfaces.

Native plants change the stormwater equation. Pacific Northwest native sedges and rushes — the kind of plants now required at Sea-Tac — can absorb 10 times more stormwater per square foot than turfgrass, because their root systems are adapted to the region's wet winters and dry summers. 

They require no irrigation after establishment. They require no synthetic fertilizer. They support the native bee species — including the western bumblebee (Bombus occidentalis), listed as a species of special concern — that have co-evolved with Pacific Northwest plant communities for thousands of years and are ill-equipped to forage on non-native ornamentals.

The institutional significance is the multiplier here. When an airport — a facility optimized entirely for operational efficiency and passenger throughput — embeds native plant requirements into its permanent design standards, it normalizes ecological landscaping in the most utilitarian possible context. 

It says: native plants are not a lifestyle choice for people with garden blogs. They are the baseline standard for any responsible land management.

Sea-Tac didn't plant a garden. It changed a policy. The difference between those two things is millions of square feet of future habitat.

--Girls With Gardens