Sifting out the small particles from your bark is not strictly necessary, but it is suggested to control the composition of the mix. The amount of sub 1/8" particles varies significantly between manufacturers, from lot to lot, and even from bag to bag within the same lot. By removing all the sub 1/8" particles from your bark, then adding in the correct amount of peat moss, you are ensuring that the fine material comprises the appropriate fraction of the mix.

Indeed, some feel that the sifted bark fines can substitute for peat. You can sift out the fine materials and then add back in one part per five parts of bark in lieu of peat, if you don't mind the irony. Or if you (or your plants!) are not so finicky, you can skip the sifting altogether. I recall that Al's description of bark requirements suggests you can use everything from "dust up to 1/2" particles" or something similar, so dust sifting may be more for the scientifically-inclined to ensure consitency from batch to batch or to assist in experimentation with modified version.

Hope this helps!

-Alex

Thanks Alex, that does help! I know my peat is very fine and dust like so I thought perhaps the sifted bark fines may be better (being less fine than the peat). But it makes sense for scientifically minded people to be able to see just how many If anyone has an opinion on peat dust vs pine dust I'd be interested in hearing it.

For the 5-1-1 mix you can either sift out the fines, or leave them in. The choice really depends on a couple of things. First, what plants are you growing and how much moisture retention do you, and your plants, need in the soil? Second, how much fine material is in the particular bag of pine bark you are using?

For my own use I screen pine bark with a 1/2" hardware cloth. Nearly all of the bagged bark I've bought this season goes through the 1/2" screen, at least 90% or more I'd say.

Normally I use whatever passes through the 1/2" screen for my 5-1-1 mix, unless the bark contains a large percentage of fine (1/8" and smaller) material. If that's the case then I might screen at least some of the bark a second time with a 1/8" screen. Usually I try to keep the fine material no more than 1/4 of the total mix by volume.

I have not added any peat to my 5-1-1 this year, mainly because the bark I used this season had a significant amount of fine material.

Since both pine bark fines and peat are very acidic, and both materials retain water, I think you could use either one interchangeably in your mixes. Just try not to use too much fine material to your finished mix, unless you need the extra water retention. The more fine material you use, the more water you retain and the less oxygen you have in the root zone.

Thanks.

TYG

Great insight, thanks! Much appreciated

I don't sift my pine for 5-1-1, never have, never will... I only sift for Gritty Mix.

Hey Spaceman - Why do you feel it's more important to sift the gritty mix?