Gritty mix problem. How do I tell if the mix is too wet ?

nguyenty(9, Los Angeles)January 12, 2012

I am using A1 granite grit size 10 and I found out that its too small. I already made a big batch and now I need to amend it with more granite grit. Is there a method or rule of thumb to tell if the mix is holding too much moisture so I can adjust it accordingly?

I will be getting the a1 size 5 granite grit 1/4". This is the ideal size correct ?

I only water once a week so I used a 5 part turface and 3 part granite grit in the photos below. It has no fine bark.

From the photos you can barely tell there are any granite in there.


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nguyenty(9, Los Angeles)

I just bought the number 5 granite grit

number 10 on top, 5 in middle, and mvp turface on the bottom. Is number 5 granite too big ?

    Bookmark   January 13, 2012 at 9:40PM
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So, here is what I've learned.

My first bag of granite was A1 Grit's Poultry #10, from the feed shop, and I thought that was just about right. My next bag was from a roofing co., A1 Grit #10, it was a coarse sand, just like in your photo's, but the bag did not say Poultry; the roofing supplier said to get the #5, and this is good too. I now buy #5 crushed granite from a gravel/landscape supplier, it is nice and sharp, I use a 1/8" screen as there is some sand. I guess A1Grit has a unique sizing system?

I understand the turface can be screened to finer size on the lower end, roughly 1/16" as it runs small. The granite (and bark) can be a touch larger about 1/8" to 1/4" overall; too much size difference and the mix could separate.

I'm not sure how you'd remedy your problem with the small granite already mixed.


    Bookmark   January 15, 2012 at 1:29AM
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tapla (mid-MI z5b-6a)

Nguyenty - it looks like your Turface has already been screened? The #5 gravel looks very good - about the same size as the granite or cherrystone I use.

You're better off with the granite fraction being a bit too small than the Turface fraction, because the granite holds so little water comparatively. I think what I would do is use it as is. I wouldn't fertilize at each watering because I suggest you DO water in sips, with an occasional flush until the roots have colonized the soil mass. At that point, with an established planting, it becomes less likely you could over-water.

I would also suggest you insert a wick through the bottom of the pot at the perimeter (if plastic), and after flushing the soil or watering, tilt the container at a 45* angle with the wick down. This changes the shape of the soil that CAN be occupied by perched water to an inverted triangle, better said - a triangle standing on an apex - and reduces the volume of excess water a planting CAN hold; and, the wick increases the effectiveness of the strategy significantly.

..... not lecturing or being snotty. Think of it as a reminder to anyone following along ~ The reasoning behind the gritty mix: it provides a soil with little or no perched water that retains it's structure indefinitely. If anyone is going to build a soil similar to the gritty mix but lacking these two properties, there is little sense in going through all the effort when something like the less expensive and easier to make 5:1:1 mix would serve as well.

Really glad to see you made the effort. I hope you let us know if in the end you think the dividends justify the diligence.


    Bookmark   January 15, 2012 at 1:04PM
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Similar to nguyenty, I do not have access to Gran-I-Grite, but have found A-1 Grit available from several local feed stores.

I have not screened my turface yet, so I don't have a size to compare the granite particles to.

***Should I get the A-1 Grit No.5 (1/4", 0.25") or No.10 (1/8", 0.125)?

Al's Gritty Mix calls for Gran-I-Grit No.2 Grower (3/32"-3/16", 0.09"-0.18").

***Based on the above, what screen size should I filter through?

    Bookmark   June 12, 2013 at 10:48PM
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