Size of grit

nemo2009(8)October 29, 2009

I'm planning to use Al's 1:1:1 gritty mix next season for my (outdoor) dahlias. A trip to my feed store showed that they carry poultry grit in several sizes of the particles, depending on the size of the critters being fed (chicks, chickens, turkeys, emus--just kidding). I'm sure the optimal size of the pieces was covered somewhere in this forum, but I'm darned if I can find it (being new here). So if anyone has that information at hand I sure would appreciate your posting it. Incidentally, I'm planning to re-circulate the drainage from the containers on a daily basis, a sort of modified modified hydroponics set-up. And I'd love comments, criticisms, and suggestions on my scheme. Thanks, all.

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If I'm not mistaken, basic particle size was listed as somewhere between a dime and a BB, or thereabouts... somewhere around 1/4 to 1/8 of an inch and smaller, but nothing sand or silt sized.

The poultry grit I get is relatively small... something akin to small aquarium gravel. I recently took a few photos of my mix and ingredients... perhaps these will help for size perspective. Keep in mind, though... I only need small batches for indoor grown bulbs, so I don't buy bulk ingredients.

This is the bag the poultry grit comes in...

This is the bark I use...

A handful of poultry grit...

A handful of mixed medium...

A batch of my mix...

A Hippeastrum bulb potted in the medium...

A tiny bulblet potted in the medium...

And, another pot of bulbs in the mix I use...

I hope these photos help with particle size perspective... I only need to mix small batches at a time to plant my collection of tender bulbs. I use this medium for indoor growing, and have not tested it outdoors. The average pot size I use is between a 4" and a 10" or 12" unglazed clay pot, although seedlings and small bulblets are potted in 2" or 3" pots.

The mix contains close to equal parts of pine bark pieces, perlite, and granite chips, and works well for my indoor application. It should be noted, however, that adjustments may be necessary for use in differing climates and growing environments... and different areas will have differing ingredients that it may be necessary to substitute... such as turface, certain oil dry products, peat, etc...

Happy Gardening!

    Bookmark   October 29, 2009 at 7:10AM
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tapla (mid-MI z5b-6a)

An ideal mix would have the particles all around 1/8" in size (perched water disappears as particle size increases to just under 1/8"). If one of the 3 ingredients is larger or slightly smaller than that, it won't change the drainage characteristics too much, and in the case where it's slightly smaller, perched water will not be a problem. Changing 2 ingredients to a larger or smaller size has a considerable impact on the properties of drainage and aeration.

The problem with having the bark @ 1/8" is it's increased surface area:volume ratio increases the speed with which it breaks down, so for my purposes, I've found that if the bark is a little bigger (1/8-1/4) and we keep the screened Turface and crushed granite or cherry-stone about BB size (grower size grit or #2 cherrystone) I get the best results.

The whole idea of the soil is durability of the ingredients, adjustability, and achieving maximum water retention with the %s of ingredients you choose w/o the need to risk any perched water. That's why I always screen and am careful about size. Particle size is very important.


    Bookmark   October 29, 2009 at 9:14AM
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First, thanks to both jodik and Al for your very helpful comments and photos (nothing beats a few well-chosen pictures). I am grateful. But the more I mull over the question of the composition of soilless mixes, the more complex and daunting it seems, especially since the factors that go into arriving at a sensible recipe may interact with each other in myriad ways. The primary requirement, I think, is that the grower be clear in his/her own mind what he/she demands of the mix. For example, for some people (say, small-container growers) such factors as durability, cost, and weight are not as important as they might be for large-tree growers. For growers of a particular species, the complete elimination of perched water may be very desirable, while for growers of other species a little perched water may serve as a comforting reservoir in dry times. Setting aside for the moment the needs of the grower (for example, the size of his/her bank account or the strength of his/her back), one has to consider the needs of the individual plant species. I'm thinking of such factors as the frequency of watering (which bears on issues such as drainage rate, leaching of ions, and pore size). And while the ratio of air volume to particle volume can be determined relatively simply, the question of pore size is more difficult to evaluate. Moreover, even if pore size were accurately measured, its effect on plant performance can only be determined pragmatically.

In my own case, and compounding the above difficulties and uncertainties, is that my experience in container-growing of dahlias has been limited to one season, and the literature on hydroponic growing of dahlias is, so far as I have been able to discover, virtually non-existent, as is the cultivation of dahlias in a soilless mix. While I do have experience in growing basil hydroponically in pure perlite, I approach the task I have set myself with some trepidation. As I noted in my first post, I will be growing dahlias in 14" pots (36 of them), in the gritty mix and re-circulating the fertilizer daily (to mitigate nutrient leaching). From my reading about them and from my limited experience, dahlias in garden soil consume considerable amounts of water and prefer damp but not wet soil. How this will transfer to a soilless mix remains to be seen. I wonder (revealing my rank amateurishness) if a medium composed exclusively of Turface might do just as well as the tripartite gritty mix, harking back to my experience with pure perlite Thanks for reading this stuff, and I invite your comments, questions, and criticisms.

    Bookmark   October 29, 2009 at 3:27PM
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tapla (mid-MI z5b-6a)

I know we spoke via email, but I'm not sure if it was to you or someone else I recently offered the suggestion that there is no reason you can't leave the organic component out of the gritty mix (or a similar medium) entirely if you wish. I'm thinking that since you intend to fertigate daily, that you'll be deciding on something less water-retentive than all Turface, even if it's screened. Turface holds a considerable amount of water.

I think once you've used some variation of the gritty mix for a while, you'll find that modifications necessary to arrive at what will work best for you will come intuitively and be driven by your understanding of the plant's basic needs for air and water and the physical properties of the soil components. It really isn't that complex, especially since you already have an understanding of the physics. You'll fare well.


    Bookmark   October 29, 2009 at 4:43PM
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Thanks again for your continued encouragement, Al. I believe I will omit the bark altogether (especially since the product I can obtain locally is rather powdery)and control the water retention by manipulating the grit:Turface ratio. And I think I had better do a little pre-planting experimentation before I spring for the whole 21 cubic feet I need to fill my pots.

    Bookmark   October 30, 2009 at 1:32AM
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It's my pleasure to share photos and information... I'm glad they were helpful. I, too, find a picture to be worth a thousand words... it really helps puts things like size, type, and exactly what the reader is trying to impart, into context.

There's a lot to consider when deciding on the best path to a perfect medium... your climate, growing environment, the amount of time you can donate to care, type of plants, available products, cost... and the list goes on.

At one time, I thought I was doing alright with regular old bagged potting soil... and for certain applications, it's not the worst thing... but for long term indoor use, it just doesn't make the grade. I found myself frantically searching for a solution to the fungal and rot problems I was experiencing on a rather large scale.

Finding Al's articles was like finding a vein of pure gold in a mine! And once I had digested the knowledge contained within those articles, I knew exactly what my problems were and how to solve them. My quest for ingredients began.

It took me a long time to locate the items I wanted, but my persistence paid off. I now have a medium that suits my exact needs. I'm very lucky in that the amounts I require are small, and that the bagged items I purchase are ready to use.

I have yet to experiment with outdoor use, and until I can locate larger amounts of the necessary ingredients, I'll stick to using the medium for my indoor plant collection... which is now thriving, I might add.

The one thing I will say is that the ideas behind this medium type are solid. The science is there. The proof is in the healthy plants I have, the live and fleshy roots, and the complete lack of rot and fungi problems. Even the fungus gnats have gone elsewhere. And I'm finding that this medium is not only ideal for my bulbs, it also works well for orchids, cacti, and even the regular old spider plant I recently rescued from its pot of collapsed dirt.

Of course, a gardener must take into account quite a few variables when looking at mediums... but the end result we are all looking for is healthy plants, and that absolutely begins with the medium, at the roots.

    Bookmark   October 30, 2009 at 5:41AM
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tapla (mid-MI z5b-6a)

She should've been a lobbyist. ;o) (She's a pal, so I'm licensed to tease her).


    Bookmark   October 30, 2009 at 10:05AM
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I have the feeling I've providentially stumbled into a family of warm, generous, and knowledgeable people.

Ned (aka nemo2009)

    Bookmark   October 30, 2009 at 11:54AM
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tapla (mid-MI z5b-6a)

..... generally fairly true - lots of warm fuzzies around here, but we do have our 'otherwise' moments, too. ;o)

I often pause to take note of and give thanks for the fact that I've met so many very nice people here (especially on this forum), some of whom I can honestly say have become wonderful friends.


    Bookmark   October 30, 2009 at 2:08PM
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Tease away, Al... I dye my hair blonde on purpose! ;-)

I don't picture myself as warm and fuzzy, necessarily... I'm more of a realist. But I do value honesty, and shared knowledge when it comes to gardening, and I think there's definitely something special about people who nurture Mother Earth. I've made some wonderful friendships here... hopefully long term ones... and I always strive to share the ideas that have worked for me.

I wouldn't tout Al's Mix if it didn't absolutely work... and by the same token, I'd share its wonders even if I didn't consider Al a friend. When you find something good that solves your gardening problems, sharing it is the only right thing to do!

For the most part, the GW community is friendly and generous, although you will occasionally run into a person or two who need to be disagreeable for some unknown reason. The world is full of all kinds, as they say... and I doubt it would be the same without all those kinds in it!

If you're looking for knowledge, you've come to the right place! Quite a few gardeners here are what I'd call experts on the subject of growing, and I've learned a lot in the short time I've been reading and posting.

A family... I suppose we are, in a way... we all have the love of flora in common, and the want to share it so we all can enjoy its beauty and bounty. Welcome, Ned!

Al, you don't need a lobbyist... your mixes speak well for themselves... I just enjoy writing! ;-)

    Bookmark   October 30, 2009 at 9:11PM
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I agree 100% with Jodi, this forum is a wealth of information. Al, JaG and many others have contributed much information and experience to the list and we are all lucky to have them.

Have tried both the gritty mix and the 5-1-1 mix. both are excellent for plant growth. When i've repotted or potted up the size of the rootballs on my plants growing in these mixes has been amazing. Like Jodi, i used to use regular bagged potting mix but it collapsed way too fast and held water like a sponge and the roots suffered. Now that i use the grit mix or 5-1-1 mix, my plants do much better.

For new memebers it might be hard to find everything you need. Once you find the basic ingredients you can experiment with your plants a bit and see if they like more or less water and adjust your soil mix.

I use the same bark that jodi uses (fir bark used for reptile bedding) and it's great. Looks prescreened so no screening necessary. It coses more than big bags of pine bark but the fir bark is available all year around and is simple to use because of the pre-screening. Saves on labor for sure, but is expensive if you have LOTS of plants.

Since using the grit and 5-1-1 mixes I've not lost a single plant due to water, air, or soil issues. The real beauty of these mixes is tah tyou can use them for growing veggies, indoor plants, shrubs, trees, you name it.



    Bookmark   November 2, 2009 at 10:53AM
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starter: 1/16 - 3/32 inch (1.5875 - 2.3813 mm)
grower: 3/32 - 3/16 inch (2.3813 - 4.7625 mm)
devoloper: 3/16 - 5/16 (4.7625 - 7.9375 mm)
turkey: 5/16 - 7/16 inch (7.9375 - 11.1125 mm)
turkey finisher: 7/16 - 5/8 inch (11.1125 - 15-8725 mm)

Here is a link that might be useful: Gran-i-grit broucher

    Bookmark   April 14, 2011 at 3:23PM
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I am with Jodi and Al on this too!

The only descision I always have to make each time I look at my plants is what plant is going to go into the mix that can be kept in the same pot for a longer amount of time/years.

Both mixes do a great job! One for short term planting, and the other for long term.


    Bookmark   April 14, 2011 at 4:19PM
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