This is the sifting setup. Too-small bits into the gray bin; sifted bark nuggets into the big blue bin. The whole 2 cu ft bag went more quickly than I expected!

This is a photo of the post-sift bark nuggets, with a US quarter for size reference. How much of this looks like sap wood?

This is a photo of the finished mix, with a US quarter for size reference.

It's better than Peat Pudding, but I have a couple of questions/comments:

-Even after reading your post (well articulated), I'm still confused why you chose coir over peat. Peat is dirt cheap (pun intended), and the default formula calls for peat. Wouldn't you want your first batch ever to be a vanilla, baseline mix, from which you can deviate down the road if desired?

-That Micro "Bark" doesn't look very barky. I've seen a lot worse, but there are some shreddy particles in yours. Are there any fines in there at all? Smallish, dusty particles? Are you saying all those chunks got through 1/4" mesh? Some look like they wouldn't get through 1/2"

- I fear that sapwood (the light, splintery pieces) is going to suck up a fair amount of nitrogen fast. Be sure to include a CRF starter at the beginning or start with the Foliage Pro within just a couple of days after planting.

My 2 cents...

Not bad, not bad.

Your Perlite is excellent. I wish I still had a local source for the coarse stuff.

I, too, use Greenall Micro Bark. I screen over 1/2-inch hardware cloth and keep everything that falls through. I'm curious what you mean by "too-small bits"? - you want to include the fine bark dust to aid in "binding" the ingredients and equalizing moisture retention. The bark dust is important because the Greenall product is not composted as far as I can tell.

The sapwood is the light-colored "match stick" looking stuff that can be seen especially well in the last picture you posted. I do a hand-picking of the sapwood after screening the bark, but mostly I just make sure to add some slow-release fertilizer to offset the potential Nitrogen immobilization mentioned by Oxboy.

Oxboy, Greenall is Fir bark, which is probably why it looks shredded...it is more "furry" (haha!) than Pine bark, for sure. And this product is fresh, not composted.

Josh

Hmmmm... I have perhaps had a fundamental misunderstanding about the way this mix is constructed. In other posts, I read the PWT occurs when "soil particulate size is under about .100 (just under 1/8) inch". So I used a mesh just about 1/8". (I wrote 1/4" in my post above, but I realized that's not accurate. This is the silver mesh used in many Container Store products, for those of you who are familiar with it.)

I discarded the parts that were under 1/8" because I understood that's what caused problems with perched water. Al (Tapla) wrote: "Mixing large particles with small is often very ineffective because the smaller particles fit between the large, increasing surface area which increases the capillary attraction and thus the water holding potential." So I was expecting to mix a potting medium of primarily consistently large particles.

Have I got it backward? Was I supposed to keep the small bits and discard the large bits? Is that not the pudding people refer to?

I really appreciate the experienced growers helping me understand the principles and how to apply them. I know you see many of the same questions over and over; I want you to know I'm grateful for your continuing to come around to teach us newbies as we get here.

Yes, you've gotten it backwards.

For the 5-1-1 mix, you keep *everything* under 1/2 inch.
This mix is designed to hold a certain amount of moisture, and the fine particulate is what helps ensure consistent moisture throughout the mix.

Get rid of anything *over* 1/2 inch.

Josh

Oxboy, good pun. :-) I see online that I can get just under 4 cu ft of sphagnum peat for around $17, but it wasn't available in that quantity at that price in WA when I was there. I could only find small bags at what worked out to about double the price of the 2 cu ft block of coir. Since I was reasonably confident I was going to make some mistakes in how I put this together (as I did!), and other posts indicated the two ingredients were interchangeable, I went with the cheaper option.

For the record, here are my costs:
2 cu ft Bark $9.99
4 cu ft Perlite $36.99
2 cu ft Coco mulch $11.99
5 lbs Dolomite lime $4.99

I'm pretty sure you can buy big bails of peat from big box for cheap, but I'm not sure the quality is top notch. Quantity over quality...

Instead of peat, I just purchase a quality bag of potting mix (which is mostly peat anyhow). Then, I use 1 part of the peat-based potting mix as a substitute. Works very well, easy to incorporate, and typically brings some nutrients into the mix.

Josh

The bark looks fresh to me. Not composted. Not sure if uncomposted bark is a good thing.

Like I mentioned, Fred, that's the only type of bark that I use.
And all of my plants have done well, in my opinion.

Josh

I don't understand, how can you compost pine bark and still have it in nugget form? Composting means disintegrating and falling apart. There is no Nitrogen in pine bark to make it compostible. Pine bark, or any bark for tha mater is dead cells and has benn weathered for decades on the tree.
JMT

'Aged' would probably be a better term and I think what we ought to shoot for as Plan A in 5-1-1. Aged or partially composted would be bark that won't suck up too much nitrogen at all, but still has a lot of rigidity and integrity.

Maybe the "fresh" bark we buy is from the more inner (or "living") layers of the bark?

The bottom line is older bark nuggets are darker, more rigid and potentially breakable/crumbly. Younger bark is lighter in color, smells fresher, somewhat bendable and can be a nutrient thief in the pot. And if you wait long enough - maybe upwards of 20 yrs - the latter decays into the former by some process that is not unlike snail-pace composting.

Weathered, seasoned, bark. The pieces of bark begin to crumble until they are the texture of a typical potting mix or "soil conditioner." For the best 5-1-1, you would use a bark that is between fresh nuggets and crumbled dust. For the Gritty Mix, you would use the fresh nuggets screened to the appropriate size.

Josh

Oh I did not realize that fresh bark can be used. I always use composted/ aged bark. I have a huge operation close to me that have got mountains of all sorts and sizes. They wet it and turn it regularly so it don't combust and set the mountain behind them alight they say. I once got 5 bags from them that wasn't completely composted/aged. It was black on the outside but still red on the inside. Smelt strongly of pine. I didn't like it so I kept it under cover for 3 months and it turned out well. The red centres were all black again.
From then on I only went for the well composted/aged ones. They cautiously scrape the top layers for me when they bag it. They know I don't want the fines. I don't have to screen and my chip size is exactly how I want it. They actually do screen it in bulk but it still contains fines.
When walking past a massive mountain of fresh bark it makes your eyes water and the pine smell is overwhelming. I just figure that my plants can do better in a more stable environment like the composted ones. It doesn't smell of pine at all. In fact it smells like loam soil. The bark nuggets lasts 2 years without breaking down (that's how long I've been mixing with bark). I emptied some containers at the beginning of the season and the 5-1-1 and gritty mixes were looking the same as when I made it. I almost used it again....But I didn't :-)

This post was edited by fredman on Thu, Dec 12, 13 at 21:53