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Bark fines particle size in Al's 5-1-1 mix

I have been reading about Al's 5-1-1 mix and I'm seeing conflicting info about the particle size of the bark fines to use. In one of Al's posts he said "particulates in the 1/16 - 3/16 size range with the 1/16 to 1/8 size range favored". Other people say they screen through a 1/2 inch screen and use everything that goes through (this is for the 5-1-1 not the gritty mix). On YouTube I believe I saw someone using a 1/4 inch hardware mesh to screen. Which is correct or does it depend?

Second question, if you're using composted bark fines you should also screen out the super fine stuff or if not, don't include the peat moss/fine particles component in the mix. Right? What kind of screen does one use for that?

Third question, we have been using organic composted bark mulch in our garden for years. We have a pile that's been sitting out all winter in western Washington zone 8 so it's broken down a bit more but there are still plenty of large pieces. Can I use this if properly screened?

Thanks everyone.

Comments (11)

  • illsstep

    I had previously been screening my pine bark through a 1/16" screen (window screen or insect screen) to remove the "dust", then making the mix with 5 parts bigger than 1/16" bark, 1 part smaller than 1/16" bark, and 1 part perlite.

    (The bark I get is pretty composted, and I'd say a large portion of it is 1/8" or below.)

    The mix worked OK, but I found that if a plant had a large canopy and/or the roots had started to fill the pot, I was noticing signs of water stress unless I watered daily (and even then, some signs of water stress). So I feel that the water retention was too low (which means: not enough very fine material).

    That may not exactly answer your questions, but I hope it helps.

    margaretandplants thanked illsstep
  • mblan13

    My PBF (Agway Pine Bark Mulch) has very little dust, and is prescreened to 3/8, so I generally use it straight from the bag without screening for 5-1-1. I only sift (to 1/8" to 1/4") for gritty mix.

    If I use partially composted pine bark (like your pile) I omit some or all of the peat, depending how much fine particles are in the mix.

    I suggest making a small batch (a gallon or so) of 5-1-1 "by the book". Sift and measure everything precisely so you know what 5-1-1 should look like. Perhaps sift the first few years. Once you get used to what it should look like you can mix by eye and adjust on the fly for different plants preferences.

  • illsstep

    Also, make sure your "organic composted bark mulch" is pine bark and not hardwood bark before you use it in a container mix.

  • gardengal48 (PNW Z8/9)

    Virtually all bark mulches are derived from some sort of conifer and ALL conifers are considered softwoods. Hardwoods seldom produce thick enough bark to make their use worthwhile for mulching purposes.

  • illsstep

    Where I am, we see a lot of mulch products advertised as such:


  • mblan13

    Illsstep, They are HARDWOOD mulches, not PINE BARK. Hardwood mulch is made of entire hardwood trees, mostly the woody interior, and are not suitable!

    Only PINE or FIR bark are suitable for use in 5-1-1 and gritty mix.

  • illsstep

    Did you not read my comments? That is my point.

  • maryjozone5

    Here in Iowa we haves hardwood bark mulches at our landscaping places. They use the bark only of hardwood trees. So I can't use that. I am disappointed because I can't find pine bark fines anywhere nearby. I will try Timberline pine bark mulch (from Lowe's) and not add peat to it. Hopefully that will work.

  • maryjozone5

    where do you get your screens?

  • illsstep

    I personally have only bothered to sift through a 1/16" screen so far. I built my own screen with some insect screen and some pieces of scrap wood I bolted together (and handles for comfort).

  • mblan13

    illsstep, oops!

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