72 Microseasons of the Pacific Northwest

Bigleaf maple (Acer macrophyllum) is the largest maple in North America and one of the dominant deciduous trees in the Pacific Northwest lowlands. Its March bloom is one of the most visually dramatic botanical events of the PNW calendar: thousands of hanging flower clusters — each a 10–15 cm drooping raceme of small, fragrant, pale yellow-green flowers — appear just as the first large leaves are unfurling, coating the entire tree in yellow-green. In forests where bigleaf maples are common, such as the lower Hoh River valley, Quinault rainforest, and every west-side stream corridor, the effect transforms the landscape from the greys and dark greens of winter to a luminous spring haze. The flowers are both insect-pollinated and wind-pollinated and produce copious nectar during warm afternoons that attracts the first wave of spring insects: newly emerged queen bumblebees (Bombus spp.) are among the most visible visitors, along with emerging syrphid flies and spring flies. Anna's Hummingbirds also visit maple flower clusters for nectar. In the Hoh Rainforest, many bigleaf maples support thick epiphytic communities of mosses and licorice ferns on their bark and limbs — in March these moss mats turn electric green against the yellow bloom, creating the iconic "moss-draped maple" image of the Olympic rainforest. Key viewing locations include the lower Hoh River trail in Olympic National Park (particularly accessible at the Hall of Mosses trailhead, where maples are the canopy dominants), Deception Pass State Park, any of the west-side Cascade foothills stream valleys, and the Willamette Valley riparian corridors in Oregon. In urban areas, mature bigleaf maples are common street trees throughout the Seattle metro area, Victoria, and Portland neighborhoods.