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Part 3:Maintenance

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Pruning and Thinning

Effective fuel removal improves the fire safety of your home. To maintain a Firewise landscape, your challenge is to reduce its flammability while retaining its aesthetic contributions.

Pruning and thinning are the most important tasks homeowners can do to improve the level of safety of their homes from wildfire. Dead branches should be pruned, and dead plants removed. All plants are more flammable if not pruned periodically; fuel removal increases fire safety. The risk attached to any one plant can be greatly diminished with maintenance.


As trees grow, careful pruning preserves their appearance, structural integrity, and functional values. But pruning also maintains their ability to resist fire.

Prune at the appropriate time of year. For trees and shrubs, prune out all dead wood, and prune for structure during the winter (for deciduous shrubs) or early spring (for evergreen broadleaf or coniferous shrubs). Think about the ‘ladder fuels’ and consider removing the most flammable shrubs (like junipers) from beneath the trees in your yard.

While a hard pruning just before the fire season in the West may seem good timing from a fuel reduction standpoint, it is a poor practice from the horticultural viewpoint. Proper pruning means planning ahead----as does proper fire protection.

No more than 1/3 of the foliage of a plant should ever be removed at once. Severe pruning (more than 30% of the foliage) of deciduous plants should only be done during the dormant season. With regard to broad-leaf evergreens, severe pruning should be done during the time when the new foliage is just beginning to appear but past danger of the last frost.

When pruning, use clean, smooth cuts. Improper pruning cuts cause unnecessary injury and bark ripping. Follow pruning with a light fertilizing.

A well pruned tree heals quickly while poor pruning results in scarring and possible disease. Young, vigorous trees can withstand more severe pruning than older, weaker trees.

Pruning tree branches at least six to ten feet from the ground helps interrupt a fire's path. Remove dead and diseased branches from trees. This reduces the potential for fire spreading into the crown.

If you are unsure when the right time of the year to prune is in your area, ask your local nursery or horticulturalist. A light pruning done as a follow-up to a heavy pruning may be done anytime in the summer.

If you are pruning a plant that is not healthy, don’t remove any live wood; it needs its leaf surface in order to generate new roots. If a weak plant might increase the flammability of an area, remove it.


The thinning of vegetation eliminates continuous fuel sources and reduces, slows or stops the spread of fire. A minimum spacing of 10’ between tree crowns is recommended. Smaller plants should be kept 5-10’ apart, depending on their size.

Keep ground covers low growing. They should not exceed 2’-3’ in height, as they then generally have an understory of dead wood. Cut ground covers down to 8”-12” every other spring. Fertilize them lightly, and then water them. The result will be a full, green cover by mid-summer with very little dead fuel beneath.

  • Shrubs should be well-spaced to break up the fire ladder and keep the vegetation density low.
  • Except for formal clipped or sheared shrubs, shrubs should be maintained by thinning, maintaining size, and removing excess leaf litter.
  • Vines and ground covers can build up a heavy underbrush of dead leaves and branches, which should be removed to lessen fuel for fire.
  • Remove or mow dry grasses, weeds and underbrush.
  • A mulch over bare soil can provide many benefits while adding little fire risk.

Even in healthy landscapes, the build-up of leaf litter and other debris can give fires a chance to start under porches and decks and on roofs.