Pine needle compost might be one of the most misunderstood areas of composting. Sure, there’s some confusion about whether that take-out container is compostable, but when it comes to pine needles, there’s a longstanding assumption that they are too acidic.
Granted, that assumption is not without reason. At our cabin in Vermont where we spend our summers, I’ve had trouble starting a garden in parts of my yard because the pine needles just rain down constantly from June through September. They make great mulch but work a little too well. There’s a difference between purposefully using pine needles as mulch and covering your garden in blankets of pine needles every day.
And if you’ve spent much time in a pine forest, you know that there isn’t a lot of undergrowth in these areas. Therefore, the reasoning goes, is that the soil is too acidic for anything to grow. Really, I think it’s because pine needles are solid mulch, not because they kill everything in their path.
The soil around pine trees is indeed acidic, but that’s because they enjoy acidic growing environments. Additionally, evergreen roots tend to run on the shallow side, meaning there’s more competition for other plants to establish themselves. And because these trees are evergreen and usually don’t allow a lot of light to get through the canopy, it’s just not a great place for other flora.
So now that we’ve debunked that myth, let’s talk about whether or not you can use pine needle compost in your vegetable garden.
Using pine needle compost in your garden: Yes or no?
First off, yes, pine needles are acidic. And if you used pine needle compost exclusively, it might be too much for your veggies. But pine needles have some wonderful benefits for your garden, including as a compost ingredient.
Before you think about composting them, however, I should point out that pine needles make superb mulch, like I said before. Like most any other mulch, they improve moisture retention in your soil, stabilize soil temperature, help control weeds, and they break down slowly, so you won’t need to mulch as often.
For pine needle compost, it’s that last item that you need to be aware of. The waxy coating on the needles, known as a cuticle, makes it difficult for microorganisms to do their decomposition work. You can speed up the process somewhat by waiting until the needles are dry before you rake them up and add them to your compost heap. You can also shred them by running over them with your mower.
What this all means is that if you add pine needles to your compost bin, they may still be partially intact while the rest of your compost is ready to go. But do you need to worry about that lowering the pH of your soil?
The truth about pine needles in your compost
Even though pine needles are acidic, as they break down, they lose some of that acidity and may even approach a neutral pH.
Amy Jo Detweiler, extension horticulturist at Oregon State University, says that as long as you limit the pine needles to about ten percent of your compost pile, they are unlikely to have much impact on the acidity of your garden soil.
Ultimately, whether you need mulch or compost, pine needles are a great (and FREE!) source of materials. Just don’t overdo it.
Have you used pine needles in your compost? How do you think it impacted your plants? I’d love to hear your story in the comments.