In 2012, the Reading Fire devastated 28,079 acres at California's Lassen Volcanic National Park. Four years later, crews treated 465 acres of bull thistle, helping native plants return

The Reading Fire began with a lightning strike in 2012 and quickly became a much larger and more severe fire. After years of fire suppression had allowed ground and vertical fuels to build up, the blaze ultimately covered 28,079 acres after spreading beyond the park onto the adjacent Lassen National Forest, as per a report by the National Park Service.

The damage did not end when the flames were gone. The severely disturbed landscape created new opportunities for invasive plants such as bull thistle to spread, while native plants faced a much slower recovery.

Four years after the fire, crews saw a noticeable increase in bull thistle across disturbed lands. That became the start of a long-term effort to survey, treat and restore affected areas.

Why did bull thistle spread after the fire?

The Reading Fire burned existing ground fuel and severely affected trees, leaving additional material on the forest floor. The resulting landscape offered favorable conditions for hardy invasive plants to establish.

Bull thistle was not immediately widespread in the disturbed areas, but its impacts became more visible over time. High-temperature, severe fires can damage or reduce seeds already present in the soil, making native plant recovery slow.

Bull thistle has another advantage. Its seeds can travel long distances, allowing the plant to reach isolated areas and establish even on severely burned ground.

With native plants struggling to return, large areas can become dominated by a single invasive species. These monocultures can develop on newly exposed mineral soils where native plants are not yet able to compete.

“It’s like a big game of whack-a-mole.” Steve Buckley, an ecologist and botanist at Lassen Volcanic National Park in northern California, used those words to describe the ongoing challenge.

“Four years out [from the fire], we saw a spike in the growth of bull thistle [on disturbed lands],” Buckley reflects.

How did crews respond?

Land managers moved quickly to address the threat. Burned Area Rehabilitation projects were funded at Lassen Volcanic National Park to support site stabilization and restoration.

The work included monitoring disturbed areas, treating invasive plants and sowing native seed.

Park staff also looked for funding that could continue beyond the five-year Burned Area Rehabilitation funding horizon. Assistance from the California Exotic Plant Management Team provided additional support for restoration operations and invasive plant removal.

At the same time, Buckley and other park staff began working to strengthen the supply of locally sourced native seed. They have been harvesting local native seed and working with local and regional seed growers. Once invasive plants are treated, park staff can spread native seed across those areas to help begin restoration.

The work has involved more than simply removing bull thistle. It has also focused on giving native plants a better opportunity to return to areas where the fire dramatically altered the landscape.

What does long-term recovery look like?

For Buckley, the work cannot be measured only by the number of plants removed today.

“Success in the short term means that we’re treating what we can… teams are removing a lot of plants,” Buckley points out, “but it’s important to ask where we want to be in 15 to 20 years… we need to keep inter-generational management in mind.”

He said he is particularly proud of the “success in the improvement of knowledge and the expanding partnerships we’re pursuing” to help restore park ecosystems.

In the nearer term, he looks forward to working with nurseries in Oregon and collecting native seed to support early native restoration. Over the longer term, he hopes natural succession, supported by active restoration, will gradually phase out invasive thistle across the Lassen system.

The scale of the work is already substantial. National Park Service staff have surveyed 21,000 acres and treated 465 acres.

The effort shows how wildfire recovery can continue long after a fire has passed. At Lassen Volcanic National Park, crews are working not only to control bull thistle but also to restore the native plant communities that were disrupted by the Reading Fire.

For now, the work continues, with monitoring, invasive plant treatment, native seed collection and partnerships forming the foundation of the park's long-term restoration effort.

FAQs

When did bull thistle increase?
Four years after the Reading Fire.

How much land was treated?
Crews treated 465 acres.