It's a common practice with the only downside coming from adding known infected used container soil or adding so much peat/coir that you can't easily get your pile hot again (kinda rare).

Adding a lot of bark-based medium is generally not a great idea, but if you have an active/strong pile going and you have the time to let it do it's thing it's not a bad practice unless you're adding a huge amount.

Many of us have been adding the old potting soils to our compost for years, except if it is known to contain disease pathogens. Peat, ground bark, coir based products have not made any difference. I'm not sure why someone would think ground bark might be different then peat moss.

Thanks folks for your input! I've been propagating for 4-5 years (since retirement), but gardening ( flowers & vegetables) for 30+ years.... I'm cautious not to add anything that might be contaminated..... I use ProMix BX (peat based) for starting seeds & often times use Fafards B-3 (which is about 1/4 processed bark) for my larger containers...... Haven't noticed any issues in my compost.....

"I'm not sure why someone would think ground bark might be different then peat moss."

Bark, especially conifer barks, are extremely resistant to breakdown...especially large sized chunks used in some tree/shrub containers. Adding a lot of it takes a lot of time to break down plus additional inputs to help break it down because it doesn't do it well on it's own.

Peat takes a long time to break down, but it's particle size is extremely small and breaks/disperses easily in a mixed compost.

This post was edited by nc-crn on Thu, Dec 26, 13 at 16:54

I don't even bother with the compost bin. I just add spent potting medium to the perennial beds.

The particle size of the ground bark used in soilless potting mixes is about the same as that of peat moss. One would need to add a pretty large amount of ground bark soilless potting mix to a compost pile to cause significant problems, unless ones compost pile was quite small.

"The particle size of the ground bark used in soilless potting mixes is about the same as that of peat moss."

The particle size of ground bark ranges from 3/4" to 1/10" (and less) depending on what you're growing.

I've used a lot of mixes of container barks for trees/shrubs that are nearly half 1/2"-3/4" pine bark.

It was/is a struggle to repurpose the stuff and it's added to "long term" compost piles at the research facility or sent to the county composting facility if we're getting rid of a huge bulk (100s of containers worth at once).

nc, I have no idea what you are buying but I have never seen any potting mixes sold anywhere with particle sizes that large, mulches yes but not growing mediums. More often then not the perlite or vermiculite added to these soilless potting mixes is larger then the ground bark, peat moss, or coir that is the growing medium.

I agree with nc-crn.
There are various "Bark -Based" potting mixes, although not sold by MG and big box stores. One is promoted by a GW member (tapla) aka "Al", It is called 5-1-1 mix and consists of 5 parts small pine/fir bargs/nugets. One part peat moss and one part perlite. Then , of course, there are variations.

Here is the kind of bark we are talking about

That is mulch, not potting soil. If the seller has it labeled as potting soil they are misleading you.

I believe he referred to it as 'bark-based potting mix' not 'potting soil'. I can't imagine anyone would make or sell that unless there were plants that like growing in it. Sounds like you are finding a problem where there is none.

Seysonn, I'm an avid follower of Al's 5-1-1 potting mix and have been using it with great results.

That picture is not the bark size used in 5-1-1. I have to screen out anything that's larger than 3/8 of an inch.

hi
I grow almost everything in pots due to my extremely poor soil/nematodes. Always add it to my raised beds when I repot. Only problem I've encountered is palm fronds takes years for them to break down.. I use that quality to make containers but must throw them away when finished gary

We have a similar series of potting mixes but dedicated to growing orchids and succulents, not general potting mixes, much less for annuals.

I add these kinds of coarse potting mixes to compost piles, but often manage these for a longer time. Since I sift all compost, the surviving larger pieces would be returned to a new compost windrow.

ssmdgardener and Kim

I was talking about BARK _based potting mix, like 511. I did not say that bark is the only ingredient it it. The picture, that I posted, was borrowed from here on CG forum.

BARK SIZE:
it is recommended that the size not to be bigger than 1/2". That means like more than like 80% of it meat that requirement. If it is not consistent then you screen the big chunks out. This is not and exact science. In addition to the nuggets, they have crushed and much smaller pieces too. So with that and the peat moss that you add to it, that should take care of packing the nuggets.

I am already employing the bark-based concept in potting my seedlings. And I will use it for my outdoors pots this year. I think this is a better alternative to peat moss-based mixes. That is why I am going to try it.

Disclaimer : JIMO.