What is composted bark?

I mulch my flower beds in spring and autumn with bark chips bought from Homebase or other local garden centre. I was talking to a friend who explained that I shouldn't use fresh bark chips as a mulch as it depletes the nitrogen in the soil. Now I know this but have always assumed that the bags of bark chips bought in garden centres were composted. Am I wrong to assume this please.

Posts

  • ObelixxObelixx Vendée, Western FrancePosts: 18,132

    The amount of nitrogen they consume in decomposing is really negligible and will not harm your plants and will certainly be more than compensated by all the moisture retentiveness and weed suppression the chips provide.    The chips are just that, chipped bark.   Composted bark is finer and stringier in texture and breaks down much more quickly. 

    "We don't stop playing because we grow old; we grow old because we stop playing." - George Bernard Shaw
  • WateryWatery Posts: 388

    You say you do this every year.  How are your flower beds looking?  If they are looking good, don't worry about it.  :)

    In some ways it's a myth that you shouldn't use fresh woodchips.  It depends on what you are covering and what your purpose is.  Fresh will inhibit some seed germination for annuals, which makes it useful as a weed suppressor.   It wouldn't be good in a vegetable patch or annual bed for the same reason.  It only ties up the nitrogen of a small layer of soil and helps with good fungi/bacteria etc.  Fresh woodchips (not bark) are actually good to use around trees, shrubs and some herbaceous perennials.    https://puyallup.wsu.edu/wp-content/uploads/sites/403/2015/03/wood-chips.pdf 

    But you have been using bark, presumably are happy with how it works and how it looks.  I would say that's all you need to know.    And I believe that the ones sold at garden centres are composted at least a few months anyway.  

    I have used bark and also use fresh woodchips when I can get it with herbaceous perennials without a problem.

  • Hostafan1Hostafan1 Posts: 22,194

    Thanks to my lovely tree surgeon friend, I go through several tons of chippings every year. 

    I've tried to find the answer to the " nitrogen depletion" issue, without success.

    Evidence is , as far as I can find, conflicting. Universal agreement seems that as a mulch there's no loss of nitrogen at all. Only if dug in before it's rotted CAN, not "will" cause problems. 

    As I say, I've tried to find out conclusively to no avail. 

    Devon.
  • Thank you all for the interesting and helpful replies. I'm happy with how my herbaceous perennials are so I did wonder about the concern over using bark chips. I use the mini chips which disappear over the course of the winter and again over the summer when using them as a spring mulch. It seems difficult to get definitive information about their use but I'll carry on using them, thank you all.

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