Its a difference in how it breaks down as it decomposes. The white wood gets digested by bacteria that use up a lot of nitrogen in the process, sucking it out of the soil and starving the plant of its most important nutrient.

Pine bark doesn't lock up the nitrogen as quickly since it doesn't break down as fast, while still giving good texture to promote good drainage.

Least thats my understanding of it, I may be wrong.

That sounds good to me. I just hate bending over for an hour picking out wood, and wouldn't even be able to say why I was doing it. I was that kid in school that asked 100 questions. You know, the one the teachers hated. Thanks!

I think you got it perfect, Edymnion. That's what I was thinking and just went to refresh my memory and that's the gist of what I took away.

It was good of you to point out that with the bark it doesn't happen as quickly - but it still does happen. So, you need to fertilize frequently.

One thing I didn't find while searching, but, thought I read at some point was something to do with changing the ph during decomposition. Man, I wish I could find it, because now, I just question my memory. argh!!! LOL Does anyone recall anything about that?

Yeah, you guys covered it.
The sapwood decomposes more quickly, which definitely leads to compaction of the media,
and can potentially lead to nitrogen immobilization and even heat spikes (during decomp).
In general, it's best if the sapwood is no more than 5 - 10 percent of the bark/mulch.

Josh

Speaking of 5-1-1..

This stuff can be reused 3-5 years? When will I know it's not good any more?

Can the large pieces and woods be used for mulch around my regular garden or should they just be thrown away?

I'm 10 days and 10 containers down, a big bunch to go... Our Walmart gives the 5 gal containers for free at the bakery department...last night they refered to me as the 'bucket lady'. Don't know how I think about that!

Free 5 gallons from the bakery at Walmart? Um... excuse me... I need to go to walmart for something completely unrelated now...

Lorabell - you can use the larger pieces for mulch, no problem. In fact, my GF needed some mulch so I gave her what didn't pass through a 1/2" screen. :-)

Based on reading (not experience) 5-1-1 is primarily a 1 year use, but, can be used 2-3 years.

Tsheets is right, the 5-1-1 is meant for a single season, but can be pressed into service
longer in a pinch. Here's the main consideration to be made: particle size. If you start
with a well-composted bark product, then the bark will be completely broken down in a season;
but if you are using an uncomposted bark, such as I do, then your bark can potentially last
for several years. As we often say, The Mix will probably last longer than it would be wise to
let a plant go between re-potting (due to the root-congestion in the container).

Many of my 5-1-1 mixes don't contain Peat or potting soil at all...just fine bark dust for retention,
and then Perlite and Turface or Lava rock to add in structure, durability, aeration, and control of
the moisture retention. With these ingredients, and by using only synthetic fertilizer, my mix breaks
down quite slowly.

Josh