You can substitute pumice for granite on a size for size basis, but you might want to consider using something like 4 pumice
3 bark
2 Turface
all screened, of course.

The added volume of pumice would make up for its extra water retention. I know that seems contradictory, but since the pumice holds more water than granite, and Turface holds more water than pumice, you need to DECREASE the most water-retentive ingredient & increase the ingredient with less water retention to come out at about the same water retention as the basic gritty mix.

AL

Oh - the leftovers ........... use the screenings from the Turface in raised beds, the garden or beds, or as a replacement for sand or perlite in hypertufa projects (great for this). The bark screenings can also go in the garden, or be reused in the 5:1:1 mix .......... and the dust from crushed granite can also be added to garden soils.

Al

Thanks Al, much appreciated! One dumb question: how can I tell if what I have is pumice or granite? I got the bag a while ago, and it was a generic bag, not much info on it?

Hmmm - pumice will be somewhat porous & granite has no internal porosity ..... but the same can be said of other forms of rock, so those physical properties aren't enough singularly to define either as granite or pumice.

Al

Pumice is easily distinguishable from granite by its great difference in weight per volume. Al

Al,

what do you recommend to use as a screen for the pine bark fines?

I've looked around a bit online and have only come up with expensive gold panning screens.

TIA.

Garrett.

Garrett, "hardware cloth" (metal) is perfect for the bark.
It comes in several sizes of grid.

Josh

Josh,

thanks for the quick reply.

G.

Josh: I can find this metal screen at HD/Lowe's?

Anyone else: so I need a 1/4" screen to eliminate particles over that size. Whatever falls through will be sifted through another screen of 1/8" size to eliminate anything smaller than that?

Forgive me if this already has been asked and answered.....

But -- how might the leftovers and used gritty mix affect the native soil if thrown on garden beds? Does it cause significant changes in the pH or minerals in the soil?

The organic fraction will be consumed by soil life and 'gas-out' over time & the granite & Turface will become a part of the soil. About the only effect you'll notice id faster drainage and reduced water retention over time, if you toss a LOT of soil on your garden's/beds.

Al

Thanks, Al.

My pleasure. ;o)

Al

I'm thinking and wishing mine garden beds had some. The Hosta's I have in the beds, rotted and have nothing left of them, the one for my mom, I put in the 5-1-1 is growing well!

Nest season, changing to raised beds and will have plenty of leftovers to toss in. ;-)

JJ

I thought I'd seen in the past that some of the experienced gardeners (Al?) used some of the undesirable screenings for growing seedlings. Is that so? I can't remember which leftovers they used though.

Kookybird: I recall Al saying the Turface fines can be used for seedlings, if they remain dry (sterile) while stored.

Hi Al,

>>> The organic fraction will be consumed by soil life and gas-out' over time & the granite & Turface will become a part of the soil. About the only effect you'll notice id faster drainage and reduced water retention over time, if you toss a LOT of soil on your garden's/beds.

I would've assumed it increases water retention. Don't the smallest Turface fines also hold water internally? If so, it should be more than the granite fines would offset -- so much waste from Turface. I have fairly heavy clay-loam soil, so it probably would make little overall difference.

I think all that dust from the bark will be good for the beds in the long-term, but in the short-term will take up lots of space for the oxygen and may be a problem if all piled in one spot. It should also tie up some N in the breakdown process.

Here is what happened to mine:
I put about 1 cuft down into a small area, piled about 6" thick. It was my first batch of bark+Turface+Granite fines a few years back. The first year it repelled water quite a bit and killed the native Bermuda grass under it (I expected as much, grass needs sun). Then it got very moldy from sprinkler water and during winter. The 2nd year the mold didn't return after summer dried it out. By the third year, it looked almost identical from the top-surface view as prior years -- like nothing had changed in all that time. I went to remove a section (I was digging out for sprinkler repair) and lo-and-behold it was fixed solid in the soil. The surrounding Bermuda grass had sent many,many fine roots into it and were sucking the water dry as fast as the sprinklers filled it up. These weren't typical large bermuda roots/rhisomes normally in my soil, but very fine ones you see in young seedlings -- except they were very long and very healthy. Earthworms were already making their way into the stuff, also.

Turface fines are great for cuttings, especially since they don't break down like peat/perlite/vermiculite mixtures.

When you stick cuttings, you want them in a medium that is porous enough or a container deep enough that the proximal end of the cutting isn't covered by a film of water that inhibits gas exchange through the end of the cutting, as this promotes rot much faster. With cuttings, you're always in a ract to make a vascular connection between the roots and the top of the plant before the plumbing rots. Turface fines are very water-retentive and support a LOT of perched water. So much that I would say they are inappropriate for cuttings unless the bottom of the cutting is positioned at least 4" above the bottom of the pot, just to ensure that the proximal end is indeed above the level of perched water. If you DO use Turface fines for rooting cuttings or seeds, please employ a wick to help with the excess water retention. There is a reason we screen the fines out, that being to greatly reduce or entirely eliminate perched water and guarantee there is enough air in the soil to ensure best root health. This is doubly important for cuttings.

A well-made gritty mix, 100% screened Turface, 50/50 screened Turface & crushed granite, or any combination of screened Turface, granite and screened perlite are all excellent media for cuttings.

What I HAVE done in the past, is sow seeds on top of a very coarse medium (like I mentioned) & only cover them with Turface fines (1/8") and mist to keep the surface moist until the seeds germinate.

AL

Posted by Joe1980 on May 8, 11 :
"To screen my bark fines, I took an icecream bucket and drilled 3/8" holes"

Joel, or anybody,
Whenever I drill soft plastic, tough chads partially block the holes.
No prob if for drainage. Yes prob for screening.
Unreasonably laborious to remove chads.
Also, removal processes result in holes larger than chosen gauge.
To drill every hole twice, the first time smaller, is not a solution.
Yes, second drilling removes chads -- and it makes new ones.