November 27

1 - Pine tree needles turn brown and fall off this doesn't necessarily mean your tree is unhealthy, and they can be used as beneficial mulch.

Q. I have noticed that many needles on the inside of my pine trees have recently turned brown and are starting to fall. Is this a disease or drought? What can I do? Since the needles are falling, are they safe to use to mulch my garden?

Bernalillo County

A. It is a regular event for needles on the inside of a pine tree (the older needles) to turn brown and drop from the tree. I checked with Cheryl Kent, Bernalillo County Extension Horticulture Agent, who told me that she was seeing many pines dropping their 3 and 4 year old needles now. This is probably what is happening to your tree. Even though pines are evergreen trees, they do not keep their needles forever. Older needles fall away every year, but the loss of old needles is more apparent when the needles falling were produced in a year with a favorable environment for the development of many needles. If many needles developed 3 or 4 years ago, then the needle drop is much more apparent than if there were relatively fewer needles formed that year. These needles are safe to use as mulch around most plants and especially perennial plants in your garden. Because pine needles contain high levels of resins, they repel water and decompose much more slowly than leaves from most deciduous trees. Their shape also helps them avoid becoming moist and composting rapidly. This makes them especially useful in areas where you will not be digging frequently. The fragrance of pine needles on sunny days is also an added benefit when they are used as garden mulch. Some people fear that pine needles are too acidic for use in our gardens. This is not a concern in New Mexico; added acidity is beneficial in our soils. Even so, their slow decomposition slows the release of their acidity into the soil. They are definitely beneficial as mulch. They are very slow to compost, so they are often better mulch than compostable material.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!