Soiless components that hold moisture?

PicTatler

Hey guys I am new to the site so I'd like to say hi to all! I'm trying to come up with a loose free draining mix that holds enough moisture for water loving tropicals. I would love to get my trees out of thier current peat base mixes and in something alittle more proper. My problem is that I have such a hectic schedule in the summertime(70+work hours a week) that I really don't have time to water twice a day. There's a few products that I was wondering if any of you guys use in your soil mix to hold more moisture. One product I've seen is lava rock which holds 40% it's weight in water, anther is pumice(which I thought was the same as lava rock, but looks different)which holds 25-50% it's weight in water and another product is vermiculite(not sure water to weight %, supposedly it holds alot) and there's one product that I've found that says it holds 150% it's weight in water it's called dyna-Rok 2, it is made for horticultural purposes and made buy dyna-gro, but it may hold to much moisture, it says it's granular and provides drainage and prevents root rot. I think it is some sort of sedimentary rock. I may make a mix of lava rock, pumice, vermiculite and partially decomposed pine bark, this may be alittle more moisture retentive than my last soiless mix of pine bark, shale and turface. If any of you guys have any insight on these products or any good moisture retentive granular mixes please let me know. Thanks!
PicTatler

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Bonsainut

Sounds like you have done your homework, all that is left is experimention.

Hey where did you get those water holding percentage figgers?

And welcome

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Keep growing,---'Nut



Lethal Use of Farce

PicTatler

Bonsainut, thank you for the warm welcoming the percentages were taken from the descriptions of the products on various sites that sell these products. I can probably simplify things and get rid of the pumice and vermiculite and just use the lava rock, dyna-rok 2 and pine bark. We'll see how this works. I haven't ordered it yet but I'm intreseted to see what dyna-rok 2 is like.

BonsaiGreenhorn

I have a mix that I bought from my local nursery that they use on a lot of their trees.

Pine Bark
Lava Rock
Turface

I havent used it yet, I plan to soon though when I repot many of my newer bonsai. So i cant really give you solid facts from myself. But since im in South Florida and the Nursery uses that mix I can assume that it must hold moisture pretty good if they use it down here. I hope this helps some. Good Luck!

-Evan

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gnarlywood

Greetings PicTatler,

Rather than "% of it's weight of water held" I suggest you determine how many "ounces H2O per quart of component held".

You fill a pot by volume, NOT weight. 10% of something that weighs 3 oz per quart (like perlite for example) doesn't sound like much, but that quart of perlite holds about 10 oz. of water. (I'm not a perlite proponent, as I don't care for the white in the mix - not appealing to my eye. Fine for material in training, though.)

I'm experimenting with water retention capacity. (I hope others can post any measurements they have performed, and that we can settle on a "standard procedure" as many variables affect the numbers wildly.) I apologize to those in metrically measured countries. I'm not a metrological chauvinist.... just not great at juggling the conversion.

For the first series perlite, agricultural charcoal, pine bark, pine cone charcoal & 'Dryzit' (like 'OilDry') were used. I have ordered pumice and lava rock for the next series and will include turface, sphagnum peat and others if located.

All materials were sifted to remove fines below 1/16 inch. The Dryzit particles were 1/8" max, agri charcoal & perlite 1/4" max as that is how these products came. The pine cone charcoal was 3/8" max and the pine bark was 1/2" max. (I prefer 3/8" max, but the bark supply lately has been very scant on the smaller pieces! I wouldn't have gotten diddlysquat from a 3 cubic foot bag!) Smaller pieces would retain better. I'm searching for a new supply and will retest pine bark.

Each material was dried (except perlite, which was newly purchased and so light anyway) in an oven for 12 hours (sorry, couldn't find the thermometer, so I cannot state the temp. It was below 450 as the bark did not scorch). I measured one quart of the heavier materials (above 6 oz/qt) or two quarts of the lighter material (less than 6oz/qt) and weighed each sample. Larger samples would reduce measuring errors, but my oven is not so big.

Each was soaked in water (more than needed to cover - the 'floaters' were held down with a lid) for 24 hours, then allowed to drain for 6 hours in a standard plastic quart pot with screen covering the drainage holes. Each sample was weighed. The difference of the wet weight and dry weight gives a fairly good measure of it's water retention capacity.

These are the results:
Dryzit 3.5 oz/qt.
Pine bark 7.25
Pinecone charcoal 9.75
Perlite 10.25
Agri charcoal 12

I was quite surprised that the agri charcoal held more than the perlite!! I repeated every measurement at least twice, but I'm going to redo it's test in the next series. I DO recommend charcoal if you can make it yourself, but consider the retail agri charcoal pricey.

I calcined some perlite with pine cones embedded in it (source of pine cone charcoal) which turned it all black or very dark grey. This will be used in some of my mixes in smaller pots where the weight of the tree & mix won't crush it excessively. I'll compare it's water retention in the next series.

Some may think the minimum of 1/16" is too small, others think it's too large. Eh .... had to start somewhere....

To increase your water retention you could eliminate particles over 1/4" or even over 1/8", but you'll have to buy more material, or trade with a friend/colleague who'll use the larger stuff.

Remember - how the components shapes (perlite is mostly round, turface is angular, pine bark is generally flat chips) fit together to form the soil 'matrix' affects the capillary attraction and thus the water retention. The sum of the parts may be more, or less, than the whole.

Have fun mixing! It's repotting time!! (At least here it is...)

Gnarlywood