Come to the Annual Firefly Festival

Long Branch Nature Center in Glencarlyn Park is built on land once owned by George Washington and features two ponds populated with turtles and frogs, fox and flying squirrel sightings, and an incredible canopy of trees  — making it one of Arlington’s most quietly extraordinary natural spaces year-round. But for one magical night each summer, it becomes the setting for the annual Firefly Festival, when the park’s wooded meadows and creek edges come alive with the blinking patterns of thousands of Photinus pyralis — the common eastern firefly — and families spread blankets in the dark to watch one of nature’s most enchanting displays. The festival, organized by Arlington County Parks & Recreation, combines guided nature walks along the darkened trails with hands-on activities about firefly biology, light production, and the environmental conditions that support healthy firefly populations. Park naturalists explain how to identify different firefly species by their flash patterns — a genuinely surprising amount of complexity lurking inside what most people experience as pure childhood magic.

The festival typically takes place on a Friday or Saturday evening in late June or early July, timed to coincide with peak firefly activity in the Mid-Atlantic region, and draws hundreds of families from across the county for what has become one of summer’s most anticipated community events. Admission is free; parking is limited along S. Carlin Springs Road, so arriving early or biking via the Four Mile Run Trail is recommended. The surrounding Glencarlyn Park — 100 wooded acres along Four Mile Run — offers additional summer programming through the nature center, including wildlife identification walks, junior naturalist programs, and creek exploration days. The full Parks & Recreation seasonal calendar, including the annual Firefly Festival date announcement, is posted at arlingtonva.us/ParksRecreation each spring.