(This post originally published 8/15/19 and updated 6/14/21)
Do they really? Today we’re debunking this myth.
With the internet and social media, we have tons of information at our fingertips, but sometimes this information isn’t totally correct. Today we’re going to be clearing up the common myth that using pine needles as mulch can make soils acidic. People have been led to believe that pine needles can lower soil pH so much that plants will not grow as well (or grow at all). Luckily, this just isn’t the case.
Pine needles do not make soils more acidic! Read more to find out why.
The pH Scale
Fresh pine needles, right off the tree, typically have a pH between 3.2-3.8. Although this is on the lower-side of the scale, using even freshly fallen needles on soils will only drop the pH slightly. If a change happens at all, it still will not be a big enough difference to damage any plants.
Oftentimes you will not be using fresh pine needles. They are usually off the tree for quite some time before you are raking them up or buying a stack of them. Upon hitting the ground, pine needles will immediately begin to breakdown through decomposition by microbes. This process neutralizes the pH of the needles. Generally speaking, the pine needles you’re using have already started to neutralize. So unless you’re picking and using needles right off the tree, there’s no possible way for them to lower your soil’s pH!
Pine needles are often raked and gathered into bales and referred to as pine straw. We carry rectangle pine straw bales at our Garden Center.
Watch how pine straw is baled!
It’s a great addition to any flower or vegetable garden. When used as mulch, pine needles help keep the moisture in, suppress weeds, increase soil porosity and eventually add nutrients back to the soil as they continue to break down. This can save you a lot of time when it comes to weeding, watering and fertilizing. We recommend that you lay a thick layer – at least 2-3 inches thick. If weeds grow through, add a thicker layer.