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.

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

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.

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

http://www.southernmulch.com/product-details.php?product_id=dghb

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.

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

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.

where do you get your screens?

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).

illsstep, oops!