"that held about the same volume of water as the average between the Turface
>and granite",

"Each of the ingredients in the gritty mix is actually carefully chosen. Particle size, the ability to hold/not hold water"

"I've been using the gritty mix for about 15 years, and haven't found a way to improve it yet"

From what I take from this, I would say the bark serves a very useful purpose and is indeed needed, just my thought.

I suppose you can grow in anything you want the way you want in anything..
I have grown plants in just pebbles, peat alone, bark alone, sand alone and so on. They only did well for so long though..
I am currently growing a jade in just "turface" and a christmass cactus in just turface and granite because I ran out of the bark fines at one time, and needed to plant quick and for now they seem to be doing well...

For some reason though, the christmass cactus and jades in the gritty mix seems to be doing a heck of alot better than the ones in just turface and granite...:-)

>From what I take from this, I would say the bark serves a very useful purpose
>and is indeed needed, just my thought.

But what role is it playing that is not fulfilled by the turface/granite mix?

"that held about the same volume of water as the average between the Turface and granite"...

I would say that the bark balances everything out because it does not hold as much water as the turface and more than the granite.. A perfect compliment to both..

I could be wrong, and maybe Al will come a correct me if need so..::-)

Mike

I've grown many plants in nothing but 100% screened Turface or perlite, so there's no doubt that you can grow perfectly healthy plants in a mix of screened Turface and grit. I include the bark mainly because of the pH factor and it is far less expensive (and lighter) on a per volume basis than Turface or granite.

What I would expect is that you would need to fertilize a little more frequently, and you might need to slightly favor the presence of the granite a little more than the screened Turface.

Al

Thanks Al.

If one did eliminate the bark (with the adjustments Al suggests), would there still be a need to replace the substrate at root pruning, or could you just reuse the (unchanged) turface and granite? interesting.

not to be disrespectful ['damn whippersnappers wanting to tweak my 20-yr-honed recipe before they even try it' ;-)] it's just that i can't see 'throwing away' a product that is 2/3 inorganic and intact just because the 1/3 organic is getting tired. know what i mean? if the primary contribution of the bark is to lower pH, could you get the same effect by adding a little more vinegar to the fertigation or just keeping a layer of bark at the top (or does the bark have to be intermixed for other reasons)? waste not, want not. cheers

Lol - I'm not selling soil here - I'm selling the idea that you need to look out for aeration first when it comes to container media. I fussed around for a lot of years & came up with a soil that works best for me, and probably for quite a few other folks too; but, that's no clear indication it will work best for you, though it probably would be a good leaping off point.

I don't reuse the gritty mix. It's usually full of fine roots & not worth my time to fuss with it. I ESPECIALLY don't reuse it if there's any evidence of oxalis, spurge, or pearlwort in it. YMMV

You MAY not even need to add the vinegar. Because you flush the soil each time you water (hopefully), the upward pH creep normally due to alkalinity in the irrigation water should be much slower than if you were using a heavy soil and watering in sips. Remember, it's the pH of the soil SOLUTION that is most important, so your fertilizer also plays an important role in pH mgmt.

Al

OXALIS! thank you! that crap is in ALL of my pots and i did not know what it was until i googled the pest names you list above. nasty stuff. i also didn't know about vinegar to prevent high-pH-induced nutrient deficiencies (and MANY other things!) until i discovered this forum recently, but i think vinegar will be with me to stay. my well water is liquid rock. the pH is not super high (7.6) but the alkalinity is significant (214) and the general hardness through the roof. i assume based on other posts i have read that my level justifies vinegar to counter soil solution pH creep. we'll see. this forum has opened up a whole new world that i look forward to learning more about and experimenting with. thanks so much Al!!