The Ember Resistant Zone. We are reinforcing a concept that is critical to homes and structures that have survived wildfires: Zone 0: The Ember Resistant Zone, or the first 5 feet from your home or structures. Pay special attention to the 5 feet immediately around your home. This area should be designed and maintained to keep fire or embers from igniting materials and spreading fire to your home. Ensure yard debris and dead plant material does not accumulate in this zone. No vegetation is recommended within 5 feet of any structure. No landscape mulch or wood chips. Use clear soil, rocks, gravel or concrete. No Trees.
https://ucanr.edu/…/Prepare/Landscaping/DefensibleSpace/i