It's all about "The Ladder". I work with Cal Fire and am constantly seeing how to eliminate ground to aerial spread. You want all brush removed from around trees, no debris and as much 'dirt' as you can manage. Trees are pretty fire proof down around their trunks, hit their leaves and branches and all bets are off. Limb up to at least 6' above the highest point from the ground/grass/brush. Best thing is bare dirt/low green grass no bushes. 100' tree clearance from structures if you can swing it.
