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Environmental Stewardship News

Posted on: May 25, 2023

Please Don’t Pick the Field Mustard! Help the Endangered Island Marble Butterfly Thrive

Environmental Stewardship Update (2)

SAN JUAN ISLAND, WA. May 25, 2023 – The San Juan County Department of Environmental Stewardship asks the local community to refrain from picking field mustard (Brassica rapa), a critical plant for the survival of the endangered Island Marble Butterfly (Euchloe ausonides insulanus). The Island Marble Butterfly is one of the rarest species in the region, and its existence is dependent on the availability of field mustard for its lifecycle.

island marble butterfly by Karen ReaganUSFWSField mustard, a common plant found on San Juan Island, serves as a primary food source for the butterfly's caterpillars during their crucial growth stages. Right now, you’ll see its yellow blooms in the prairie areas on the south end of the island. Watch for signage alerting you to protected zones, and please refrain from picking field mustard - by removing this vital food source, we inadvertently contribute to the decline of the species.

Photo credit: Island Marble Butterfly by Karen Reagan, USFWS

Media Contact: Angela Broderick, Climate and Sustainability Coordinator,, 360-370-0537

About San Juan County’s Department of Environmental Stewardship   

San Juan County’s Department of Environmental Stewardship is responsible for solid waste, marine resources, clean water, cultural resources, and climate and sustainability work.  The department offices are located at 1609 Beaverton Valley Road, Friday Harbor, WA 98250. For more information about San Juan County’s Department of Environmental Stewardship, visit


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