Gritty mix - New Zealand question

maca9April 4, 2013

Hi all

I'm based in Auckland and am keen to try Al's legendary gritty mix.

I can't find some of the ingredients so wanted to some experienced views on best substitutes.

Options I have in addition to the pine bark (1/4 to a 1/2 inch) and peat are:

Pumice -
Perlite -
Vermiculite -
Fine scoria -
Nutrifield Clay balls (hydroponic)

Can I ask what of the above would be best used for both the 5-1-1 or the gritty mix?

My use is solely potted citrus trees in an outdoor setting with full sun.

Also in terms of size I understand its ok for the bark to be a little larger than the other materials in the mixes. Is 1/4 to 1/2 ok or is that getting to big?

Also for the other materials they are all 1/4 or a bit smaller. Is that ok?

I understand that these options or sizes might not be perfect but hopefully they will be able to produce a mix which is better than my current off the shelf heavy peat based potting mix.

Thanks all


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greenman28 NorCal 7b/8a

Howdy, Macca!

For the Gritty Mix, you want the bark to be 1/4 inch (with pine bark, 3/8 of an inch max). The durable ingredients, such as scoria, pumice, and perlite would be the best substitutes in the Gritty Mix, but the ratios of the ingredients will need some adjustment.

For the 5-1-1, bark ranging in size from 1/2 inch down to the fine bark dust is used. With peat and perlite and the bark, you can make this mix.

My oldest Citrus - a Moro blood orange - is growing in a mix of bark, perlite, and red lava rock (scoria), so I know from experience that this will make a suitable mix. It does quite well in a terra cotta container during our dry California summers. However, during the first season in the mix, be sure to pay attention to watering - if your ingredients are somewhat large and lacking in fine material, the mix may drain and dry rather quickly. Just keep on top of it, and by the second season, the mix should have "bound" together nicely and will go slightly longer between waterings.


    Bookmark   April 4, 2013 at 10:17AM
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Hi Josh

Thanks for the quick reply.

You mentioned that scoria, pumice, perlite would be good for the gritty mix. I assume this is with the bark still? But you suggest that ratios would need to be tweaked?

What would they need to be tweaked to if I used those?

What ratio is your bark, perlite and scoria mix Which is working well for citrus?

Thanks for your help.



    Bookmark   April 4, 2013 at 2:54PM
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greenman28 NorCal 7b/8a

Now you're going to put me on the spot ;-)

Al (Tapla) is really best at figuring ratios, and maybe he'll stop by and see this. In the meantime, I'll give it a shot and gladly acquiesce to Al's advice should he appear.

1) Yes, Bark is the basis of the mix, the main filler. The perlite and the scoria hold moisture, but also maintain durability and structure to build aeration and drainage into the mix.

Now, it's been a while since I made the Moro mix, and I honestly don't recall the exact amounts of each. With the ingredients I used, I made a fast-draining "gritty 5-1-1." When I look at the mix currently, it looks like 4 - 5 parts screened fir bark, 2 parts Scoria (red lava rock), and 1 - 2 parts perlite. I'm going to link you to the Thread documenting the process...hopefully you can make some sense of it ;-)

Greenman's Moro Blood Orange


    Bookmark   April 4, 2013 at 8:45PM
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tapla (mid-MI z5b-6a)

How about some input as to the relative and actual sizes of the components - especially the scoria?


    Bookmark   April 4, 2013 at 8:48PM
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The pumice, perlite and hydroponic clay balls are all 4mm-8mm in size.

The scoria is 5mm-15mm.

The pine bark is 7mm - 14mm.

Hope that helps. I appreciate all the input.



    Bookmark   April 5, 2013 at 12:05AM
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tapla (mid-MI z5b-6a)

The ideal size of the ingredients for the gritty mix is about 2.5-4.5 mm. You can use some of the larger ingredients if you wish, but at least .667 of the whole should be ingredients in the 2.5-4.5 mm range. That isn't to say you can't USE the larger size particles, but you'll be giving up a lot of potential desirable water retention because of the larger pore space associated with the larger particles.

Josh sent me a note asking me to ck this out for you before you sent an email. Sorry to take so long getting back, but I've been really busy & I'm behind on my mail - at least a week. Be sure you tip your hat to him. He works hard to help everyone & enjoys every minute of it!


    Bookmark   April 6, 2013 at 2:19PM
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Thanks Josh. I really appreciate all the help. It's been a very steep learning curve these last few weeks!

Ive gone for the perlite/pumice/bark mix you pointed me to. Looks great! Hope I can have the same success with it.

And thanks Al for the comments on particle size. I know your views are extremely in demand so I'm not surprised your behind a bit in emails!!

Definitely I had too much media above 5mm so I've now purchased a 5mm seed screen and its perfect!

If the pumice/perlite/scoria can't get through it does make the cut. Haha.

The bark will be a bit bigger but I understand that should be ok if the other 2 are all in the right range making up the 67%.

Cheers Guys.


    Bookmark   April 7, 2013 at 4:04AM
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rexedwardfairy(Zone 11)

Hi Al & Josh

I'm just reading this as I'm an Aussie and like NZers can't get 'turface' but have just found I CAN get red scoria. I've been using Al's 511 for about two years. I've never screened the bark size bc I was too lazy. I think this has resulted in mixed results (as you'd expect) with the 511. Nonetheless, i STILL like it better than potting soil!

I've decided that this year, with some of the plants that arent faring as well in the unscreened 511, to transplant them into SCREENED GRITTY mix.

Now there is no way I can get the bark down to 5mm size - they just dont make bark that small here. So I'll commit to leaving the bark at 10mm-15mm size. And I'll screen the scoria and the perlite to a 5mm size. That's all cool.

What I'm questioning now is the whole 511 ratio for the gritty mix. It seems to go out the door if I'm to ensure 2/3 of my media is 5mm or smaller size.

AM I RIGHT IN THINKING my ratio for gritty mix will now look a bit more like a 111 - ie

1 - pine bark (sized 10mm-15mm)
1 - red scoria (screened to 5mm)
1 - perlite (screened to 5mm).

Hope my question makes sense. And thank you for answering if you find the time.

    Bookmark   February 8, 2014 at 2:43AM
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