A resident reported the fire around 10 p.m. on Saturday in the 8800 block of Geysers Road, which is just north of Cloverdale, fire spokeswoman Melinda Crabtree said. The fire was contained just after 4:15 a.m.
Several units responded to the scene but had a hard time enclosing the blaze because it was dark and in an awkward location, Crabtree said.
Firefighters could only estimate that between 10 and 20 acres burned, she said.
No injuries were reported and the cause is under investigation.