“There has been a lot of activity and a lot of work from firefighters to protect the trees,” said Nancy Phillipe, Yosemite park ranger and fire information officer.

Firefighters working from planes and on the ground in difficult terrain race to surround the blaze before it destroys the towering trees that have inspired generations of hikers and attracted tourists from around the world.

Workers even went so far as to place orange sprinklers around the base of the Grizzly Giant, one of Mariposa Grove’s most iconic redwoods. The moisture from the mist provides a “preventive first aid” measure if the fire gets too close, according to ecologist Garrett Dickman. “We really don’t want to leave this one up to chance,” he said while standing at the base of the tree in a recent Facebook video.

So far, none of the named trees in the grove, including the 209-foot Grizzly Giant as well as the Bachelor and the Three Graces, have been damaged, according to Phillipe. The fire was 25% under control by Monday evening. The cause of the fire is still under investigation, she said.

The lack of wind also helped keep the fire away. “If it becomes a wind-caused fire, it’s all over,” said Stanley Bercovitz, a spokesman for the US Forest Service. “It has the potential to be much worse.”

Gargantuans, which can live for thousands of years, only grow in about six dozen groves along a narrow strip on the western slopes of the Sierra Nevada. Normally, the giant sequoia can not only thrive in the midst of low-intensity wildfires, but it needs them to survive. Its fibrous bronze bark resists burns and insulates the interior against the heat of periodic fires. Its tiny seeds can only successfully take root in soil left bare by a fire.

But the recent fires, fueled by vegetation killed by a scorching drought and built up over years of fire suppression, are testing the mettle of nature’s most massive trees.

“We have catastrophic fires on a scale we’ve never seen before,” said Joanna Nelson, director of science and conservation planning for the Save the Redwoods League. “We have seen a very large increase in the extent and intensity of fires and damage in giant sequoia especially since 2015.”

A lightning-triggered wildfire last year came dangerously close to General Sherman, a tree that is the world’s largest by volume and older than the Colosseum in Rome, before firefighters rolled up blankets fire retardants around him and other giants from Sequoia National Park in California to just southeast of Yosemite.

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Other giant sequoias weren’t so lucky. A total of three fires in the past three years have killed up to 19% of the entire population. An early melting of the Sierra Nevada snowpack in May only supercharges dry conditions this year.

The Washburn Fire in Yosemite is also on the doorstep of Wawona, a community of about 160 people within the park that is home to campgrounds as well as the historic Wawona Hotel. Normally swollen with tourists in the summer, the area was evacuated following a mandatory evacuation order on Friday.

The fire casts a pall of smoke over much of California. The haze blotted out vistas of popular Yosemite destinations such as Half Dome and El Capitan. It has grown so large that the Bay Area, about 150 miles away, was choking under an air quality advisory on Monday due to smoke.

Past fires can help stop the current one. Officials said the fire will be slowed as it approaches the footprint of a 2017 fire.

“That’s fine with us because what we’ve seen in the past is that when unwanted fires enter a footprint area, they tend to slow down,” said Yosemite park ranger Phillipe.

For now, she urged visitors who are still flocking to other parts of the park to be patient as the south gate remains closed: “There is a greater impact on these other entry points since this one is firm.”