Pine Needles – A Prickly Issue

It’s time to clean up the yard for summer –  What should we do with all these pine needles?

Landscaping in Flagstaff always presents its fair share of challenges, regardless of the time of year. When pine trees are a part of your landscape design, they make for some recurring issues for homeowners and landscapers both. Here’s the low-down on pine needles and how they can affect your outdoor living spaces.

Why do pine trees drop their needles? 

Unlike deciduous trees, which shed all their leaves at once, a pine loses only a fifth to a quarter of its needles each year. Chlorophyll breaks down, and about half the nitrogen, phosphorous, and other elements in the needles moves into other parts of the tree.

What are the hazards?

  • Excess buildup of needles around houses and buildings can be a fire hazard. The increased temperatures and dry winds of spring turn needles into tinder, so it is important to properly dispose of the needles before the summer heat.
  • Large accumulations also prevent moisture from reaching the soil, and smother grasses and flowers.  


How do they affect my soil?


  • Acidity:  Pine needles have a pH between 3.2 to 3.8, indicating high acidity. However, pine needles break down at such a slow rate that they have little effect on soil pH. 
  • Drainage: Pine needles don’t add nutrients to soil, but they do increase soil porosity so oxygen can better reach the roots. The needles lock together easily, which means that, when coupled with water, the mulch stays in plays and won’t wash away even when used on slopes.  Pine needles break down more slowly than other organic mulches, requiring only about 1 inch replenished material annually.

What should be done?

  • Safety First:  Create a defensible space around your house. This means raking up and discarding all needles next to your home and deck, including drives and walkways.
  • Mulch:  Consider using needles as mulch in your vegetable garden. Because this type of garden is kept fairly moist, is often located away from the house and consists of plant material that is not particularly flammable, fire danger is greatly minimized.  Needle beds should be used only on isolated beds and not as a continuous cover.

It’s important to make informed decisions with regards to your landscaping, especially concerning safety issues.  Call me with any questions, or call your local fire department with specific questions in assessing the hazards around your home.  Our next article will provide some helpful tips for creating an aesthetically pleasing and functional fire-wise landscape.  

Sean Andersen

Mountainscapers Landscaping


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