Pine needle mulch #735128

Asked December 09, 2020, 11:17 PM EST

I read on the Oregon State University site that it is a myth that using pine needles as mulch would have much of an impact in lowering the ph of the soil.  The article continues to say, that as this is a myth, one should not worry about planting under pine trees, as the soil will not become acidic and harm plants.

I wanted to ask the question about whether pine needles cause the soil to become acidic in the opposite manner.  Rather, would the acidity of pine needle mulch be a more beneficial mulch in beds where one has plants that favor acidic soil (i.e. azaleas or rhododendron)?  In other words, would a pine needle mulch be beneficial to my azaleas, more so than a wood or other mulch?

Johnson County Kansas

Expert Response

Thank you for your question. I assume that this is the article to which you are referring: As the article says, adding fresh needles will temporarily reduce soil acidity, but, once soil microbes begin to decompose the needles, the acidification process is largely reduced. So, you can certainly add them to mulches with other components, but do not count on longterm effects. Here is another OSU article addressing azalea care, with more.longterm soil amendment recommendations: Good luck!
An Ask Extension Expert Replied December 10, 2020, 2:04 AM EST

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