Ask Al a Question forum: Material size for Al's Gritty Mix

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Aug 6, 2013 9:23 PM CST
Does the size of the individual components really make a huge difference?

If I use the granite and Turf at the approximate same size but have larger bark will the soil be unusable? What if I screen out the larger pieces of bark but leave stuff in there up to 1/2 - 1 inch in size.

I will be planting Pulmeria and Citrus trees in containers so they can be moved indoors during the winter.

Any help would be greatly appreciated.


Aug 21, 2013 7:26 PM CST
Name: Rick Corey
Pacific NorthWet Zone 8a
I think that, even with trees, chunks 1" in size mostly just wastes volume in the root zone. And if you have enough big chunks and few enough fine grit and fibers, your water retention will drop near zero. I hope you have drippers so you can water four times per day!

Even 1/2" chunks may be hurting more than helping, by wasting space that roots could otherwise fill. Think of them as 1/2" pebbles or small rocks. Wasted space.

If you're aiming for fast fast FAST drainage, just reduce the amount of fines that you add, say below 5%.

Why not use everything that passes through 1/4" hardware cloth after you pus it around for a while with the back of a steel rake? Or maybe remove the fines that pass too easily through 1/8" hardware cloth?

Then run the 1/4" + fraction through a chipper or lawn mower, and re-screen them. I've wondered if "pounding" then rubbing big chunks might give flakes, long chips and longer fibers (instead of near-spherical grit).

If you really do want some bigger chunks for some reason, use 1/2" hardware cloth and don't rub it at length to get as much through as possible. Just let the mulch roll down the screen at a 25-30 degree angle, and stuff much smaller than 1/2" will fall through rapidly.

Pieces with some dimensions slightly less than 1/2" but one dimension larger will fall through slower, and tend to roll off the screen before passing through.

After doing a "rough cut" rapidly with 1/2" screening at an angle, you can re-screen each fraction by slowly sieving with 1/8" or 1/4" or 1/2" mesh to recover more fines, or remove more coarse chunks, so that you have a more uniform size distribution (which will maximize your usable open space).

[Last edited Jan 22, 2014 4:04 PM CST]
Quote | Post #999229 (2)
Sep 5, 2013 8:03 AM CST

Thanks for the help. I will run the pine bark through a 1/4 mesh and go from there. I will then take the rest and see about running a lawn mower over it to reduce the size.


Sep 9, 2013 1:33 PM CST
Name: Rick Corey
Pacific NorthWet Zone 8a
Cool. I sometimes wonder if I could get a more fibrous, less chunky result if I hammered the larger chunks.

The bark chunks hold VERY little water, which is ideal when I use small bark nuggets to "amend some commercial peaty mix to the point where I only use 10-15% of the peaty mix..

But I wonder if I could replacee even more or the peat mix by using more fibrous bark - coarser than peat fibers but with one dimension less than 1 mm and another dimension less than 2-3mm. Hopefully with a long dimension 5-10 mm.

I might need to use a cheese grater.

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