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Took down 13 eastern white pine trees and was left with a significant pile of chips (plus lots of millable wood for flooring and other projects).

I have several mature perennial beds and am planning to create a new one (~30 meters long) from divisions and new acquisitions in the former pines’ footprint. I’m considering some fruit trees in addition to shrubs and perennials.

Are pine chips suitable as cover for perennial beds? Is acidity an issue? Are there other issues (chemical, landscaping-wise) to be aware of? I saw in some of the similar posts, potential concerns for runoff. If it is a problem, are there proven ways to mitigate that? I have a lot of extra metal edging that I was planning to use on the downward side of the beds.

Happy to answer any questions that might help people give detailed and accurate answers to this. I’m in zone 6A.

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The pine woodchips will make an excellent mulch. See this informative, scientifically based fact sheet from Washington State University for more information. Note that it's a free download.

To immediately answer a few of your questions with quotes from that linked paper:

  1. Is acidity an issue?

No. In field situations it is difficult to significantly alter soil pH without the addition of chemicals. Temporary changes in pH may be found in the decomposing mulch layer itself, but these have little effect on underlying soils. Significant changes in soil pH can only occur after decades or centuries of mulch use.

  1. Are chemicals an issue?

The only chemicals that I can think of here are allelopathic chemicals such as juglone (in black walnut). As far as I know, pine contains no allelopathic chemicals, but even if it did:

Many living, growing woody plants contain allelopathic chemicals, which can prevent seeds from germinating or kill young seedlings. Most compounds have no effect upon established plants. Cedars (Thuja spp.) have not been found to have this ability. Even Juglans nigra (black walnut), the best known allelopathic species, has not been shown to have negative effects when wood chips are used as a mulch.

By "runoff"are you referring to people saying that chips float downhill? I can answer from experience that bark will float, colored chips available from garden centers or box stores will float (because they're actually ground up pallets), but chips and shredded bark will NOT float. I've used both on a 7-10% grade with no problems at all. In any case, chips certainly prevent soil runoff due to heavy rains.

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  • This makes sense. Do you have any idea why people are always saying that pine chips will alter the soil or hurt plants? I have a similar experience with burning pine for firewood. Many people around here believe, wrongly, that pine isn’t suitable for wood stoves because of the sap. Is it just the kind of thing that becomes received wisdom? Even experienced gardeners whose advice I trust pooh-poohed the use of pine chips.
    – jwwz
    Jul 9, 2022 at 15:00
  • Your take on it being received "wisdom" is, I think, the correct one. That, combined with our "this guy on the internet said [whatever wrong information is the trend of the day] so it must be true" social media. In the case of pine and pH, because pine needles CAN lower pH a little and that very locally, I think that then (il)logically turned into - "if pine needles lower pH, then they lower it a lot and so using pine wood chips would REALLY lower the soil's pH". There is a ton of non-scientific, just plain wrong horticultural information out there (continued)
    – Jurp
    Jul 9, 2022 at 21:59
  • The "Argument from Authority" (en.wikipedia.org/wiki/Argument_from_authority) plays a part, too, but the problem here is that the authority people use often doesn't know what they're talking about. The guy in the UK who popularized putting cardboard on your garden is just a TV presenter, not a horticulturalist. Putting cardboard on your garden actually kills the soil by preventing oxygen exchange between air and soil (it essentially suffocates aerobic life in the soil). Because he's on TV, he's an "authority", so people follow a practice that has been scientifically proven to be awful.
    – Jurp
    Jul 9, 2022 at 22:07
  • I’d not even heard of using cardboard as sheeting. Does the same (suppressing aerobic life) hold when using newspaper to suppress weeds? I had some friends who were planning to do that in their vegetable garden and would like to point them in the right direction.
    – jwwz
    Jul 10, 2022 at 0:07
  • Yes, if the newspaper is layered as sheets (it's fine if shredded). Here's a link you can reference: gardenprofessors.com/the-cardboard-controversy - use your browser's search facility to look for newspaper in the comments. There are 200+ comments on that article, and the author responds to all of them. IIRC, there's also a link to the study that supports the author's conclusions. FWIW, I use cocoa bean hulls in the tomato section of the veggie garden, and a no-till approach in all of it. This eliminates most weeds over time (without tilling, only last year's seeds will sprout).
    – Jurp
    Jul 10, 2022 at 1:49

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