Earth Notes
9:36 am
Wed October 7, 2009

Earth Notes - Pine Needles

Flagstaff, AZ – We all learned in elementary school that evergreen trees don't lose their leaves. Most conifers, including majestic ponderosa pines, are evergreens. By staying green all year long, these trees can photosynthesize anytime conditions are good. They don't have to spend valuable energy adding leaves once the weather warms.

But, as anyone who lives in a ponderosa pine forest knows, these evergreens do lose their leaves or, more accurately, their needles. Once a year, usually in autumn, bundles of ponderosa needles turn brown and drop to the ground.

Unlike deciduous trees, which shed all their leaves at once, a pine loses only a quarter or a fifth 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. A tree that loses more than a quarter of its needles at once may be suffering from air pollution or some other stress.

Ponderosa needles have a waxy, impervious coating that helps them withstand drought. They decompose slowly. Some can last a decade or longer before they completely break down.

Excess buildup of needles around houses and buildings can be a fire hazard. Large accumulations can also prevent moisture from reaching the soil, and smother grasses and flowers.

Wise homeowners rake up needles every so often, then put them to good use along garden paths, as mulch, or woven into pine needle baskets. They know it's a blessing to live amid the Southwest's great ponderosa forest especially with a rake close at hand.

By Rose Houk