Are Pine Needles Good Mulch? | Almanac.com

Are Pine Needles Good Mulch?

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V. Shulikovskiy/Shutterstock

Can you use pine needles as mulch?

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Many gardening myths die hard but none as hard as the idea that you can’t use pine needles as mulch because they are too acidic. This old wives’ tale has been debunked many times. Don’t be scared! If you have access to free pine needles, by all means rake them up and use them liberally on your garden. They not only make great mulch but are a good addition to the compost pile as well.

Pine Needle Mulch: It’s All Good

Pine needles are light and fluffy making them easy to work with. A 2- to 3-inch layer works best for keeping weeds at bay during the growing season. Water can still pass through easily since the needles don’t mat down or form an impenetrable crust. Because they lock together they will stay put on a slope and won’t blow around too much or be swept away by heavy rain. The needles are long-lasting and natural-looking. Much nicer than dyed wood chips!

My white pine needles are about 4 inches long and do the job but longer needles like those on Ponderosa pine or Longleaf pine are the best for quick coverage.

  • Ponderosa needles are 5- to 10 inches long and grow in clusters of 2 or 3.
  • Longleaf needles can be up to 14 inches long and are a very popular mulch, especially in the southeastern US where the trees are native. Its needles are raked up and sold in bales or bags as pine straw.

Pine needles last on the tree for about 3-4 years before they drop so every tree is losing 1/3 to ¼ of its needles a year, usually from late August through October. That’s a lot of free mulch and no need to cut the trees. Talk about a renewable resource!

Heather plants insulated with pine needles for wintering. Credit: V. Shulikovskiy

The Acid Test

The fresh needles have a pH of around 3.5—pretty acidic—but by the time they fall, they are dead or dying and have already begun to break down. As they slowly decompose and are digested by soil microbes their pH becomes close to neutral. A mulch of pine needles will not lower the pH of your soil. You would have to dig a large quantity of fresh needles into your soil for them to affect the pH. If pines are thriving on your property your soil is already on the acid side or the pines wouldn’t be so happy there. The trees and their needles did not make the soil acidic.

Still worried? Put down a layer of compost before topping it with mulch.

The only place where pine needles would not be recommended as mulch would be in fire-prone areas. They burn fast and in a windy wild fire flaming needles could be blown around and spread the fire even further. Shredded bark, wood chips, or straw also are not good choices to use where fire is an issue. Stick to non-flammables such as river rocks, stones, or gravel.

Learn all about how to mulch your garden in our Mulching Guide!