I use pine bark in my potting mix like everybody else but I really don't know WHY it has to be pine bark.
Since Pine bark fines decompose faster than hardwood fines, why don't people use hardwood fines?
Is there a problem with them? Do they harm fig trees? Does it change the PH or give off a toxic substance?
If there is nothing wrong with them, then why don't we use them in the potting mix?

Bump. I've been wondering the same thing.

Me too, even posted the other day... No answers

I thought it assisted with the PH levels but I don't recall for sure.

I would say it doesn't have to be Pine. Either should be composted a little before use. I believe it has more to do with availability.

Here's my experience as well as what I've learned from others.

I use hardwood bark mulch in my potting mix all the time. But I also used peat and pine bark mixed in. I get large bags of pine bark (fines) from Lowe's that are labeled as "Soil Conditioner". All it is is ground up pine bark.

I've read that some garden veggies can be grown in pure pine mulch with great results. Not the same with hardwood mulch. It's apparently all about the chemistry between the types of wood.

Here's what I've learned a friend of mine who is a horticulturist as well a soil chemistry specialist. Hardwood mulch doesn't improve the soil over time. When it breakdowns and "burns out" it hasn't added any lasting nutrients to the soil. When pine mulch is used it improves the soil nutrients and leaves an overall improved soil condition even after the mulch is "burned out". I have no way of proving this myself but this is basically what my buddy told me.

I also just learned this. When using lime in your soil, lime doesn't break down into a usable form unless the soil is already acidic. It takes some level of acid in the soil in order for lime to begin to breakdown. Once the soil has reached a neutral PH, or just above, the lime is no longer breaking down. Thus it would stand to reason that there is no real benefit to adding an excessive amount of lime at anytime since, once the soil reaches neutral, no more lime is needed. This is all just some side points that may be only marginally related to this topic but thought it might be helpful to share.

Not sure if any of this is helpful or not but there you have it :-) . 

Tonycm, In fact, you can use hardwood bark as a potting medium for the most part. Walnut is an exception I am aware of, even when composted. There is a big difference between pine bark & hardwood bark in terms of managing your figs & other plants growing in a mix with hardwood bark. There is a significantly lower level of lignin in hardwood bark than pine or fir bark. So, hardwood bark breaks down more quickly in a potting mix than pine bark. Also, because pine & fir bark have a low pH, you typically need to add lime to those potting mixes to raise the pH which assures a supply of calcium to the plant.

You may find the attached PDF from the horticulture group at North Carolina State University helpful in making your potting mix decisions. There are several pages discussing pine & hardwood barks starting on page 11. Enjoy!

That is a great PDF.  I believe the key reason is on page 13.  Hardwood bark contains large amounts of cellulose.  Microorganisms in the soil that decompose cellulose work quickly and require large amounts of nitrogen.  This results in a lack of nitrogen available to the plant growing in the medium.  By contrast, in pine bark, there is not much cellulose, but a lot of lignin.  Lignin decomposes much more slowly, so the nitrogen is not depleted. 

I suppose that if you fed your plants regularly with a liquid fertilizer, you could mitigate this issue, but I've never tried.

The reason for this question, as I see it, is not which is better, it's a question of availability and cost. I can get pine bark mulch at $250 per yard bagged (on sale) or I can get nice partly decomposed mulch $17.00 per yard. By adding $20 of ozmacote I think the case is closed.

Anyone know about desert tree mulches. We have palo verde, mesquite, sissoo, various ash trees? I'm using this mulch but don't know if its good.

DWD2, I didn't get a chance to read the whole article but from what I did read it seems that pine bark is the way to go. Hardwood can be used but it seems to have more negatives than pine, along with depleting nitrogen and decomposition rate. So now I know WHY we use it in our mixes instead of hardwood. Finally a reason as to why we use it instead of "because that's what I was told to use".
Thanks for posting the info.