Any source of N will do. Urea, Ammonium Sulfate/nitrate, urine (if you are so inclined), blood meal etc.

The N simply provides what the bacteria need to break down the wood (that and temp/moisture)

Used coffee grounds, some starbucks give them away.

I know the answer is variable depending on temperature and moisture but would it take more than the summer to get pine bark mulch composted? I'm being naive here but the closest thing I can find to "pine bark fines" (even soil conditioner) is bags of pine bark mulch I saw at Lowe's. Was going to call around to friends and see if anyone had a shredder and use that in containers. Wondered if it was "composted" but bag didn't say so assume it's not. I'm desperate here for this ingredient for container mix and running out of time for this year.

Can't even get nurseries/vendors who carry brands like Fafard to order it. They don't need or want a pallet of the stuff.

While the bark can be composted you are probably better off purchasing a cheap shredder than composting to get it to the size you want.

Heck, if you don't mind screening just use a lawn mower with a mulching blade and bag attachment. Run over a pile of pine bark chips and call it a day. If too much is too large, run it over again ;) Screen it through 1/4th inch hardware cloth and you are good to go for the 5:1:1 mix for one-two year plantings. Screen it again through window screening (1/16th inch) and you have a product suitable for the gritty mix.

Anything too large for the hardware cloth either run over again or use it as mulch. Anything that passes through the window screen put in a garden bed.

Thanks, Justaguy2. I thought the bark needed to be composted so as not to negatively effect the nutrient balance and/or drainage.

Going to call a couple friends tomorrow as I'm pretty certain one of them has a shredder and buy those bags of pine bark mulch I saw at Lowe's.

Other ingredients available in large bags at nearest Agway.

You've SAVED my containers for this year with this one response!

I can stop making myself crazy over this. :)

I thought the bark needed to be composted so as not to negatively effect the nutrient balance and/or drainage.

The composting or not composting is not important. Particle size is what is important.

The idea behind partially composted bark is that much of it is of a small particle size. The smaller the particle size the more water it can hold and the less oxygen.

For annuals and water pig plants this is very suitable as it will retain ample water while still providing top notch aeration for a season or two.

For longer term plantings we don't want the smaller sizes, but larger. The idea is the larger the pieces the more aeration and less water retention. This means favorable aeration is maintained longer. The larger particles would go into the gritty mix and be suitable for 3+ years.

For those wishing to stretch their dollar as far as possible I offer these thoughts:

A commercial, peat based mix is ideal in a deep (but not shallow) container for 1 season, but can probably be reused for 2 without a serious decrease in plant performance (results will vary widely depending on the mix, some aren't even suitable for one season).

A bark based mix of smaller particle size is ideal for 1-2 seasons, but can probably go 3 without a serious decrease in plant performance. Not a good choice (after year one)for plants in very shallow containers or those with a known aversion to 'wet feet'.

A gritty mix consisting of 2/3rds inorganic media that will never break down and larger particled organic stuff that will, can last almost indefinitely without a significant decrease in plant performance. For super picky situations such as very shallow containers with plants that can't tolerate wet feet at all, limit to 3 years of use.

It all boils down to particle size. The smaller the mean particle size the more water the mix will hold and the less oxygen it will hold.

At one extreme is clay sub soil. Super tiny particles. Too small for the eye to see individual particles. At the other end would be 1/2" rocks.

In the clay sub soil put into a container almost nothing would survive. Too little oxygen, too much water.

In the container filled with 1/2" rocks almost nothing would survive. Too little water and more than enough oxygen.

The idea is to find a balance between the two and to choose materials that will resist break down/compaction for at least as long as the plant will have to be in the media.

Thankyou. I have a bag of blood meal that I never used. I thought also that if you use uncomposted pine bark in the 5.1.1 it could tie up N? Thus partially composted was to be prefered. filix.

The bark isn't likely to tie up N because it decomposes slowly. In a composting situation adding N will speed the process up, but it still won't be a quick thing.

Thanks justa. Your right. it must be if the uncomposted pine bark has too much sap wood in it. Then the wood uses N as it breaks down. If I was going to grind my own up, I would buy those nuggets, because their 100% bark. filix.