Hi Guys

Nev. the pine bark we all get for potting mix is referred to as, seasoned pine bark, meaning it is aged, turned regularly for about 6 mths to leach all the tannins out of it before it is used, they don't actually 'treat' it with anything.

Pinkbroms

Hi Nev,

Re Ross's point about seasoned bark, another one of the issues with fresh bark can be nitrogen drawdown, ie the way the microbes that decompose the pinebark actually use up the available nitrogen, leaving little available for the plant. This effect is much stronger with fresh bark than it is with bark that already has a decomposed layer on its surface. I used to see this dealt with pretty often in orchid literature, but I haven't seen it mentioned much in the context of broms. The link below might be worth a read.

From memory (which may not be totally reliable), I seem to recall native orchid growers composting their pinebark by turning it in a pile as Ross indicated, but with the addition of a few handfulls of urea, so there is extra nitrogen to support the microbes so they can decompose the outer surface of the bark as quickly as possible to reach a stage where further decomposition and nitrogen consumption is much slower and more stable. This shouldn't mean there is a lot of free nitrogen floating around after the bark is composted, just that if you put some in to fertilise the plants, it isn't all gobbled up immediately by the microbes.

As I understand it, the pinebark sold around here for landscaping is generally not composted and is a fresh brown colour, while the pinebark that is sold for potting is normally already composted and has a dark earthy (but still firm!)surface texture.

Hope this helps and is not too much sucking eggs. I'd also be really interested in other people's thoughts on nitrogen drawdown with broms.

Cheers, Paul

Here is a link that might be useful: nitrogen drawdown

Yes i agree ,the Pine bark is generally only composted ,and you can do this yourself but it takes time ,yes i know its cheap to use " decorative bark mulch" but its not very good ,and why do it ? I used to do it myself years ago ( out of neccesity ) and used to mix blood and bone and Dolomite with it, water it well and then turn it all over at intervals as it composted ,but as its available now this way i dont bother ,I get mine from South Australia ,comes from Van Shaicks " Bio Grow " i use the one called Orchid mix ,its a quality product ,and suits all but Crypt's ,Nitrogen draw down is no use for any plant ,it certainly does no good for root establishment either to use non composted bark ,Ph is not that critical as whatever the Ph of your water supply is ,that will soon be the Ph of your potting mix ,( that does not mean its not critical for some plants ,you just can't control it depending on you water supply ) " Brunnings " Cymbidium Orchid mix is a good Bark based product and is very suitable for all but Cryptanthus ,Cheers, Jack

The whole point of using conifer bark is that it is much higher in lignin and suberin than other organic products. The lignin gives it its structure while the suberin prevents it from being broken down by microorganisms. The result is a stable product that breaks down very slowly. Slow decomposition = low nitrogen immobilization. I use and prefer fresh conifer bark because it breaks down slowly and has a longer lifespan than partially composted bark which already has one foot in the grave.

I'm quite confused by the need to add organics. If I stick broms in my native, sandy soil (that has few organics) they do quite well, usually better than my potted broms. Of course, I rarely put broms directly in the soil (Pitcairnias are the exception) for a number of reasons.

Hi all,

Just to add a little bit more info. to this discussion, I found out yesterday that a chap who previously worked at what was then "Wondabah Orchids" in the Sydney area, now makes and sells various bark-based orchid potting mixes and the bark he uses is treated with something to age it much quicker than having to go through the normal composting process.

I also found out that he sends a lot of these mixes to Queensland orchid growers, so maybe one of our members from up north might have some idea what he uses.

It just seems a good idea for those of us who don't have the space to compost larger quantities of bark.

All the best, Nev.

Hi Nev,

Since a very important part of the composting or ageing process is to provide the conditions, and the time, for the microbial populations on the surfaces up to the bark to build up to a plateau level so that subsequent nitrogen drawdown is relatively slow and stable, I guess it is a surprise to see that someone has come up with a super-quick way of treating bark, (ie quicker than the conventional adding of water and a nitrogen source to accelerate composting), and still be able to avoid very high nitrogen drawdown as soon as the bark gets into the nice, moist environment inside a pot and the microbial populations skyrocket.

Then again, I am frequently surprised and quite enjoy the process!

Cheers, Paul

Hi everyone,

Kerry, now that you're back on the air again maybe you know what sort of pre treated bark they use up north. I've seen it mentioned in some of the brom journals, but you know what it's like, when you want to find where you read it, you never can , hence the question

All the best, Nev.

Sorry Nev, I know little about what sort of pre-treated bark is used anywhere in particular. Many of the commercial mixes are sold and distributed over several states by chain outlets.

Brom growers in northern N.S.W. and Queensland use various recipes of ingredients - those who make their own might know more about the treated/seasoned bark.
I know some folk in South-east Queensland use a substance called "clinker" in their growing media - very shell-like and gritty, and which does not break down over time.
In northern Queensland, most brom growers use a much heavier mix, and add scoria pebbles (or something like that?), which suits their growing conditions better.

I really don't think there is any standard ideal formula which is universally successful. There are so many variables to take into account re climatic and cultural conditions, that many growers find their own ideal media, through trial and error. What works well for folk in dry temperate Victoria would not likely be suitable in the northern tropics, and different again in the sub-tropics. I imagine it might also be the case for the type and treatment/seasoning of bark chips.

K :)

I agree with Kerry ,most growers have their own mix ,same as Orchid growers ,my experience is that if you have 12 different growers , you'll have 13 different mixes ,all said to be the Panacea for every plant ,what works for you is what works for you ,but its best to always use a QUALITY product ,more expensive to start with ,cheaper in the long run ,
Jack

Hi again everyone,

The first question I posted was not about the cost of mixes, but what other methods of treatment the bark or indeed the bark in the mixes were given to age it, aside from composting. The reason being that a lot of growers use bark which is primarily marketed for orchid growers (in fact I have never seen a bark or mix in my area specifically marketed for bromeliads). I got the answer I was looking for from the Orchid Forum when one of the growers gave the ingredients for the treatment, and my suspicions were right, I shouldn't be rushing into buying this aged bark with out knowing the process it goes through or whether it has been tried and tested by other growers first.

The answer to my question was as follow:

Posted by arthurm NSW AUST (My Page) on Fri, Apr 23, 10 at 1:18

Here is a recipe. Not recommended. Too much trouble and probably cheaper to buy a commercial product.
"PeterÂs" formula for soaking bark to treat one 50 litre bag
Urea - 130 Grams

Dolomite - 35 Grams

Potassium Sulphate - 25 Grams

Ferris Sulphate - 35 Grams

Copper Sulphate - 10 Grams

Soak bark in this mixture for 10 days. Treatment provides some nutrients and reduces acidity so that orchid roots are not damaged.

As arthurm says "probably cheaper to buy a commercial product" The point I'm trying to make is that even if we do buy a commercial product, some barks in fact could have been treated with chemicals (including copper) during the treatment process and although not harmful to orchids, I have had bad experiences with copper on bromeliads in the past and I personally am now extra cautious. The other thing is of course, that as some of the commercial mixes list some of the major ingredients such as wood products, sand, peat, perlite, fertilizer, wetting agents etc. while others don't, and as yet, I've not seen any reference to whether or not the bark has been treated initially with chemicals and what, if any traces may remain.

I didn't mean to "stir the pot" with my questions, but just thought the info may be worth considering when selecting the bark you use in your mixes.

All the best, Nev.

I don't think copper would be on my list.

Hi Nev,

Those nutrient ratios for nitrogen, potassium, calcium and magnesium (from the dolomite) and iron look reasonably in balance for something that you want to give a big nitrogen hit to try to compensate for drawdown and leave a bit for general fertilising, but a couple of things are a bit weird:

1. If you're trying to leave a bit of general fertilising capability, what happened to the phosphorus?

2. That amount of copper looks way way way over the top to just make it available as a nutrient (even broms have to get some). I wonder what they are trying to do with it - use it as a fungicide / bactericide as for treated timber?

I think I'll continue to do a "Jack" and get properly composted stuff from top-line suppliers. Thanks for the warning!

Cheers, Paul

There are several methods of treating bark for growing orchids in particular. Some just use fertilizer and dolomite - I will have the recipe for a tried and tested method in the next few days. It is used by some of Australia's best known orchid growers. Will post when I have it.

Here is the treatment mix used by several well known orchid growers/nurseries for treating raw bark - the formula is for treating a 75 litre garbage bin with 70 litres of bark in it.
180 grams Dolomite
70 grams Urea
20 grams Iron (Ferrous) Sulphate
15 grams Potassium Sulphate
Place bark in bin, add chemicals, fill with water, let soak for 7-14 days, then drain and rinse thoroughly - ready to use.
Use the dark liquid on the lawn - will quickly green it up.

Thank you very much for giving ideas on how to treat pine bark before using as orchid mix. Pine bark here in north Philippines is free, but I need to remove resins that is supposedly dangerous to orchids. Thanks much. I will try and see results. hope not to sacrifice my orchids.