The largest wildfire of the year in California is now threatening one of the state’s natural treasures.

Flames from the stubborn Rough Fire have reversed course and are now closing in on Grant Grove in Kings Canyon National Park, The now-evacuated grove is named for the towering General Grant tree, which stands more than 260 feet tall and is the second largest tree in the world by sheer volume.

Grant Grove is home to about 50 giant sequoias, some of them 3,000 years old. The trees are naturally resistant to fire, but given the stress inflicted by four years of drought, parks officials are trying to mitigate the risk. They are clearing away brush from the bases of sequoias and even setting up sprinklers to wet the forest floor.

Even closer to the flames is an area called the Converse Basin in the Sequoia National Forest. That’s home of the Boole Tree, the sixth largest tree in the world.

Lightning strikes at the end of July sparked the wildfire east of Fresno. It’s burned through 110,000 acres, or more than 170 square miles. It’s grown 25,000 acres in the past week and id still only one third contained. Some 2,200 firefighters are tackling the blaze and evacuation orders remain in effect for a number of towns, including Dunlap and Pinehurst.