Carson City firefighters had to quickly extinguish a fire behind Greenhouse Garden Center off Curry Street before high afternoon winds spread it up C Hill.
Battalion Chief Richard Chrzanowski said the fire appeared to have started in a pile of bark, known to spontaneously combust when tightly compacted in storage.
"That product is prone, under perfect conditions, to ignite," he said.
Because fire would burrow under a bark pile, firefighters had to pull the pile apart and the wind carried embers to other areas of the yard and reignited previously extinguished piles.
Crews were on scene at 1:10 p.m. and cleared by 3:30, said Chrzanowski.