Do Pine Needles Make Soil More Acidic? Truth or Gardening Myth?

Hi Back in the spring I made a video about
planting blueberries, and because blueberries like an acidic soil I talked about various ways you can
bring down the pH of your gardening soil. And one way I mentioned was to use pine
needle mulch. Now, I heard back and in one of the comments from MrChipGardner who has a YouTube channel as well, and he said actually pine needles don’t bring down the soil pH and he gave me links to two sources: one
from Washington State University and one from the Forest Industry Council and because this is quite different from what I’d heard in the past I decided as Stephen Legaree for his
thoughts on the topic Stephen is not only a biologist but he
also has extensive experience working with the Boreal forest in Canada so I thought I’d ask Stephen to appear on
video today to answer some of my questions about pine needles and soil acidity. So, to start off, Stephen, do pine needles bring down the soil pH?
What a great question Patrick. So, I’m standing here in the boreal forest of Canada in order to answer your
question Pine needles do not actually make soil
acidic. They are themselves acidic however this is a
common misconception. Even universities like Cornell University makes reference to the fact that pine
needles cause acidity in soil That’s incorrect. Although the pine needles
themselves have a pH about 3.5, they don’t decay and transfer that to the parent
material. By the time they are decayed enough to transfer anything, they’re at a neutral pH of 7. Okay, but if pine needles don’t increase acidity, why is it that pine
forest soils are usually more acidic? Well, that’s very interesting question, Patrick. In fact, You’re correct. The soils in the Boreal forest are acidic, but it’s
not because of the pine needles themselves. The pine needles are acidic on the tree but what happens is they fall to the
ground, and they don’t transfer that acidity at all.
Now, the Boreal forest characteristically has a
very large canopy. What that canopy does it – it means not a
lot of this beautiful sunlight actually makes it through. So, we have a dense canopy, high volumes of rain also happen in this area, which means we’re limited in the in the
microbial activity that occurs within the soils and decomposition happens very very
slowly. With the increased precipitation and slow decomposition what happens is
the water moves through the column very slowly. A major feature here in the Boreal
forest is bogs and fens, which are
characteristically defined as where water either stays or moves exceptionally slowly
through the system. And as that water leaches through that initial A horizon – so the organic on
top – what it does is it takes with it a lot of I had the buffering
capacity of most soils. In return, the longer that water stays in
contact with the parent material below that it
releases acidic elements, meaning that top organic
material ends up being acidic, and it’s not at
all due to the pine needles that that fall and decompose as part
of that. what if I were to, say, mix the pine
needles into the soil and possibly speed up the decomposition process? Would that help with the transfer of the
acidity to the soil? What a great question. Even if you
combined the pine needles into the soil itself it
simply doesn’t break down fast enough to transfer any of that acidity to the surrounding soils. Well that was
very interesting Stephen. Thank you so much for taking your time
to share your expertise on this topic. I think is something that’s going to
generate some discussion, so i hope to hear from viewers in the comment section
below as to what your thoughts are on the topic of pine needles and soil
acidity. Well that’s all for now. Thank you very much for watching, and
until next time remember you can change the world one yard at a

76 thoughts on “Do Pine Needles Make Soil More Acidic? Truth or Gardening Myth?

  1. when you have a very low "3.5" pH pine needle drop to the soil it gets wet and a molecular chain(what once was alive and collecting molecules from the air/water faster because of the pH) breaks off and rebinds with the surrounding soil molecules allowing for a greater rate of rebinding(of hydrogen or lowering pH) until this rate stabilizes. The pine tree roots also release a lower pH from their epidermis(root bark) further stabilizing the lowered ph to inhibit other plants as a strategy to out compete other plant forms. In this it is very efficient!

  2. I have a lot of pine and blue spruce trees on my property. Last year, I ran out of potting soil. Instead of buying another bag, I decide to see what would happen if I made potting soil out of 50% dead, dried pine and spruce needles and 50% dirt from under these needles. I planted a tomato plant I had grown from seed (Pruden's Purple Heirloom potato leaf variety). The result was that it was one of my best producing tomato plants last year. Hardly scientific, but my plant did not die, it was my best plant and it produced very well.

  3. I love running through the forest, which we are lucky to have a huge urban park, Pt. Defiance only 5 miles away. The smell – the soil. So, I decided to try a test. Under my huge pine tree in my front yard I decided to do a small compost. Grass clippings, dry leafs (which I got from the park) and all the pine needles from the tree. This spring I have the most amazing compost! I also used coffee grounds (Thank you Starbucks). I hate the fight with slugs. I heard slugs love Hosta. I have 3 of them under my pine tree, which are surrounded by pine needles. I used to rake them up to make the flower bed look nicer. Now I leave them to deter slugs. I too thought the pine needles were acidic but all the plants seem to do great. I am going to use pine needles around my plants to try to keep away the slugs because the needles are sharp. This video cleared up some of my thoughts about the needles. I love your videos and also Stephen's. Both show much knowledge and scientific facts than a lot of them. Plus, I live here in Tacoma and Washington University is right here. I more could I ask for? Thanks for the info.

  4. I heard it was due to the types of fungus which decomposing pine needles have a relationship which which as a byproduct creates an acidic environment… perhaps this is over a very long period like in a pine forest so not useful in the home garden.

  5. What about adding pine needles to compost piles with higher N to C ratios that speed the decomp up to less than a month? Would that add acidity to the finished compost pile?

  6. I live on a N.E. Texas on a pine tree farm, and my neighbor has a pine tree plantation (thousands of acres). I was wondering is to much pine needles
    (straw), roto tilled in to the soil, then turned over with a double edge, deep plow going to help retain moisture? My soil is deep sandy loam, tested at already 7.5 acidic, going to be to much? It is August here now, 95-degrees, high humidity, and garden is in direct sun. Come November ,I will have plenty of hardwood fallen leaves to rake, and then added to the mix. What are your thoughts?

  7. Living in areas prone to having a lot of Pine Needles, I would always try to keep them off the garden, because I didn't think they would have anything beneficial to add to the soil or components of a garden bed. If anything, I thought they would harm the soil due to "acidity". lol So, Thank you very much for this tidbit of gardening wisdom!

  8. For all the discussion of "pine" needles, all the coniferous trees around Stephen are spruce. Probably better just to talk about conifer needles.

  9. i am a more recent follower and just found this. he is talking about boreal forests and standing among what looks to be either spruce or fir, rather than pines like we have in the south. does this apply to those as well? just curious because i just add fertilizer for acid loving plants to my blueberries.

  10. I just recently acquired five large garbage bags of brown pine needles with brown leaves mixed in! My already established compost pile is about 120 degrees at the center and going up! This video was very informative and now I will add the pine needles along with coffee grounds and grass clippings!

  11. so then what kills all growth under the damn pine trees? any plants i've planted under a pine, with access to plenty of light rain/watering. except for hardy bushes nothing grows under the pines in my yard or any home i've owned with pines. this canook is full of shit!

  12. Thanks OYR and thank Steven too, great info. I had heard differently and always passed by pine needles. Nut now I won't anymore.

  13. I've used pine straw on peonies roses and red currants. These enjoy alkalinity. They all grow great in it. Love the stuff!

  14. Thank you for the GREAT information!! I have 5-6 huge pine tress in my yards, so now I have lots of free mulch!

  15. Hello! Thank you for this vid. I have so many free pine needles as a source of mulch! Thank you that you answered my question! I can now go and gather as much as I want! Greetings from Bulgaria

  16. But if we go the other way, how do I make my soil more acidic if it's needed?
    I have increased the amount of iron, and that have saved both my lemon tree and my blueberries (specially the lemon tree after I was forced to water it with tap water during the winter) but that's just an emergency measure to keep it alive.

  17. Well ding dang! I built a hugelkulturs style bed…my berry guild…and I used pine specifically for this purpose!!! I'm thinking that the bottom line of gardening is to NOT over think things?! First time gardener here…with big dreams and plans of building a community garden to grow fresh produce for people who can't afford it!!!

  18. is there oils in the live needles in the tree that get washed off in rain that can cause the soil to get acidic?

  19. What is a good way to reduce acidity without having to buy sulfur year after year? I planted blueberries using lots of peat moss but as they grow they'll start to get their roots in more basic soil.

    Should I looking for bog soil and use it as a kind of additive? Should I use my left over lemon juice/peels from my lemon tree?

    What can I do? I'm not so much interested in organic as I am in being self sufficient any ideas?

  20. I have a lot of spruce trees and one pine tree on a vacant lot I own. One year, I had an extra tomato plant that I grew from seedling but nowhere to put it. I never had any success with tomato plants in pots, but I had an extra pot and thought I'd give it a go. Problem was, I was out of potting soil. SO I figured, what the hell. I wen under one of the spruce trees and pushed aside the 6 inches of fallen, brown, dead spruce needles and some dead pine needles as well. Underneath was a very black, rich-looking, soft soil. So I decided to use that soil in my pot, but since I needed a drainage medium I decided to use the spruce and pine needs (mostly spruce needles). I mixed the soil and needles together, about 2 parts soil and 1 part needles. Not only did the tomato plant grow beautifully with lots of tomatoes, but it was the best tomato plant I grew that year. Take from this story what you want. So from that point forward, I started using pine needles as mulch for my beds. I don't use spruce needles simply because they prick my fingers/hands when I plant stuff (I plant with bare hands). Unfortunately, I will have to cut that pine tree down someday soon as it is too large and shading too much of my property. No more free mulch 🙁

  21. Where I live in Alberta the black dirt is very clayish, you would think pine old needles would make a good ammendment, add a little blood meal if you think the decomposition would rob the nitrogen

  22. That's great to know. However, I suppose it won't hurt to mulch with pine needles. I know it's not always the case, but it's safer to err with a bit of biomimicry of the natural habitat in the garden space. Since bluebs grow come from such forests, I would imagine they have evolved with pine mulch for quite a long time now.

  23. Thank you very much please continue to spread this correct information. As an Arborist (UT-4532A) my challenge is to correct mis-guided information that has been taken as truth through "cultural knowledge sharing"

    This mis-information is a case of correlation not causation

  24. Even listening a few times, I couldn't understand his explanation of why pine forests have acidic soil. Guess I don't know what "buffering" and some of his other terminology mean. But I get the point, and it's an important one, so thanks!

  25. I had three trees and two died. So, I put Laylandii needles on the top of the soil and the plant is now thriving. So, I would say that in my pot, using tap water, the acidity washes off and makes the soil more acidic.

  26. Colorado has a lot of pine forests, and we're famous for our alkaline soil. To grow blueberries here, one must plant them with no contact with the native soil. A county extension guy recommended digging a hole, putting in a bag of peat with holes poked in the bottom, and planting the bush in the bag. We didn't like the idea of having plastic in our soil and instead planted blueberry bushes in large half whiskey barrels. They're doing well. I live very close to the mountains, and our soil has a high PH.

  27. My Thoughts are —>Well I have tried it over the years and they do make the soil acidic. I have rich soil and the needles break down very fast. But out of what he just said they do make the soil acidic… I the only one that understood that lol. You never see this in none pine forests(some smartass might say well they loose their leaves in the fall so that layer does not form)..It is like saying because you ate that spicy burrito for supper your going to have poops in the morning. And someone saying it is not because you ate that spicy burrito it is because you have a weak stomach. But sticking to the subject at hand he said the needles form a barrier which in turns turn the soil acid but not because of the needles….lol it is because of the needles. Wanna see for yourself take soil samples add needles repeat and watch. Every wonder why grass wont grow around pine trees? (again someone might say well it is because of all the mulch) take samples and see for yourself.

  28. What if you made a nutrient blend from pine needles by putting them into a blender? That should allow the acid to be mobile and transfer to the soil

  29. Good video of that, but am just confused, so if pine needles don't acidic the soil then what does? Is it the whole pine tree?

  30. One product I know that is acidic is coke,high in sugar content,is great for acid loving flowering plant like Azaleas.Try it,makes Azaleas blooms massively,blueberries should work too.

  31. Thanks for this, I am going to try to plant some random gardens in our pine tree land to see if anything grows more for fun. I do plan to add some soil additives to help a bit. Not sure if anything will grow but I feel it is worth a try. Thanks so much!

  32. Yup entirely correct. I use Christmas tree mulch that the city gives us every year for our urban garden. It doesn't acidify the soil. Like any organic matter, it'll ferment anaerobically and acidify if you bury it quite deep (it'll also stink), but that's all. As a mulch, pine stuff (bark, needles etc…) tend to make a brown humus instead of the usual black humus people get from leaves, straw or regular wood chips. But is nor worse nor better than regular humus.

  33. Thanks, Patrick! Long wanted to know about this. But here is a question about sawdust of coniferous trees. I have read many times that they can not be used for garden plants because of their high acidity, only for plants such as blueberries or conifers. And since here we have dominated coniferous sawdust, it is better not to use them at all. I have doubts about this, and I would like to know your opinion. Also, is it worth using pine and spruce cones for mulching? Thank for sharing this info.

  34. Nothing make soil acidic. It's the acidic compound salt mix in the soil that make people think the soil is actually acidic. When water sit or being soak underneath the soil it releases some of the compound. Like salt/water or sugar/water… Plants root doesn't feed off the soil, plant root feed off water… Plants suck up water from the wet soil which contain what they need.

    So where does these acidic compound come from? Rain and animals urine.

  35. Do an experiment.. a shit ton of pine needles in a compost pile and one without… mix the resulting compost with the soil from your property… one from pine needles.. one without… test soil before it is mixed with the compost.. and test it after… then test it again in a year… put these mixtures in beds and use them as you normally do so they are being used normally :).. if there is a difference you will see it in the soil tests… but if you want to lower your ph.. "elemental Sulfur"
    My soil had a lot of free lime in it. It's ph started out 8.3… it is now 6.5 and i have another area i am lowering even more to 5.5 to 6 ph. I got a head start by mixing sulfuric acid in a 55 gal barrel with water and started in the corner of the yard and started tipping them over on the sodic soil… should have seen the bubbling… then water it in and let it set for a week and do it again.. I got a soil ph tester so i could give it a quick check and i tested it down a foot deep… til it got to 6.5.. only took me a month instead of a year or two. I don't recommend others doing my method with the acid because it is a dangerous thing if you get any on you.. not for your average gardener. The soil is booming with life now.
    On the blueberry ground I dug 10 8 inch holes about 3 ft deep with my post hole auger… filled those holes with my acid mixture and kept them full until they quit foaming then slowly filled them in with soil until the ground was level again.. weeds are growing extra green in those areas now and it has been about 6 months since i did that so i am ready for my blueberry plants 🙂

  36. Could it be that blueberries, strawberries and hydrangea likes alkaline ascorbate or acidic ascorbic acid(Vitamin C)? Lot of experimenting this season. My strawberries seems to suffer heat stress, apparently studies show that treating them with foliar Vitamin C makes them more tolerant. Wonder if it adds to their own content and taste? Maybe there's a pine needle mafia going on.. LOL..

  37. Thank's to both of you , my question have answered, gotta work it now in our garden,, more power and God bless,,

  38. There is nothing more attractive or validating of one’s intelligence than to admit he/she is wrong and seek the right answer.

  39. I know this is unrelated to this video, but how often do you top dress coffee grounds in your garden?

  40. I think if you burned fresh pine branches and used the ash and bio char you would lower soil ph i think the soil in pine forests is acidic from forest fires

  41. My Thujas have died. The summer was too hot. So I used a wood chipper to cut all branches into small pieces and used that as the only mulch under my trees. Is that bad? Everybody keeps telling me that this will make the soil acid. According to Your video it won't, but are there other hazards?

  42. I just wanna know if partially decade pine needles would make a good container mulch for plants like tomatoes.

  43. I've used pine straw for many years, having lived in a pine forest where the needles are a foot thick on the forest floor. It has never raised the acidity of the soil.

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