I constantly like to look for useful products as ingredients for use in growing mediums for containerized figs, and other plants.

I recently came across bags of crushed coral mixed with small pieces of sea-shells, grits, etc. for use in salt-water aquariums.  The coarse grits seem to be the perfect size for use in quick-draining mixes.

I also came across crushed, lava rocks 1/4"- 3/8" gravel...which may also may have use in the quick draining mixes.  I found this product in a Fireplace, and Barbeque, supply store.

Has anyone ever used these products as ingredients in growing mediums.  The crushed coral might take the place of a limestone top dressing, and the crushed lava rock will aid in drainage, and aerating of the growing medium... I THINK??

The lava rock, I would imagine to be inert...but, the crushed coral would probably effect the pH of the growing medium and make it more basic/alkaline.

Please give me your thoughts.  Thank-you for your attention.

Frank

I think salt is the thing to worry about with the coral.

Seeing as coral is a possible ingredient in limestone, then I agree with you that it could act as a soil sweetener and raise the ph.  However, I'll wager that buying a bag of limestone is more economical and the result is exactly the same.

I don't agree that using crushed stone, of any kind, is an aerator or soil lightener.  It's illogical in my mind, and I'll stick with using peat moss and other organic items to lighten soil.  Small stone, and stone dust will compact rather than aerate, even lava.

A rock pile, no matter if it's giant or made up of crushed rock aerates and drains easily.  How many of us have seen trees growing out of cracks in rocks in the strangest places? 

We are amazed that the thing could even root, but it's been there a hundred years, and obviously is happy!  Between each granule of crushed granite is a tiny air pocket that allows oxygen and drainage.

Organic matter and fertilizer mixed in add to the joy of a plant in a container, but I'm a huge believer in crushed granite (not powdered), mixed with pine bark fines, turface, and vermiculite. 

I like the idea of crushed lava and coral!

Tell us how it goes!

Suzi

The crushed coral is very expensive when bought in a pet supply store.  I'm wondering if Florida Nurseries sell this product in big, 50 lb. bags?  It attracted my eye because of the very coarse granular texture, very unlike the top dressing, ground limestone, that I buy in Home Depot.  Granular, and powdered limestone, does nothing to improve drainage, in fact, it gets quite sludgy when wet.  This crushed coral will not compact, and will be as free draining as aquarium grit.

However, I cannot say anything about the salt content.  Will coral and sea shell grit retain salt?  Can I leach it out if I soak and then wash the coral grit?  I simply don't know...

The crushed lava rock looks like a very porous, "foam"...filled with little holes and spaces...very hard, coarse, gritty, and sharp.  Good for roots....plenty of oxygen, spaces for moisture retention.

If I find any more information about these two products, I will pass on to you guys.

Thanks for the comments.

Frank

As a plant gets older you want a more dence medium any way. You want it to retain moisture. 
but if your looking for a mix for cuttings stick to pine bark mulch and pearlite not vermiculite

What is the source of the coral? I'd hate to think there'd be a new source of revenue that would further damage the various coral reefs of the world.

I added lava sand to my garden to light it up a bit since I have re clay.  I think any stone, rock, shell that is hard with irregular pieces would be advantageous.  I also added expanded shale - the pieces are much larger then the lava sand, about 1/2" or so.  It its also porous so it wicks the water away, but holds it for later use.

I believed seashells and corals are calcium carbonate.

I wanted to use the properties of both these ingredients as a substitute for the gravel in the classic, quick draining mix, comprised of of pine bark fines and Turface MVP.  The gravel component would be replaced by the lighter lava rock, and crushed coral would sub for the powdered, silty limestone.  I figured the mix might be a little lighter, still retain moisture in the Turface/bark combo, be very quick draining, and pH would be more alkaline/basic from the coral grit.  All of this is just supposition, and I have nothing but my instinct to go by.  That's why I started this thread...to get opinions.

I need to containerize a few more trees and I needed to make a new batch of the Q-D'ing mix, so I was just wondering if these two new ingredients would work a subs. for the gravel. Calling Dr. Al.....

Do you think I could get away with adding some big organics like coco bean hulls, shredded leaves, etc?

Talk to me.  I'm listening.

Frank

I used a 50/50 mix of perlite and crushed lava rock (crushed it myself to 1/4" ~1/8" size) and was happy with the results. Porous (& inert) lava rocks keeps moisture and releases it as needed.

Check the ph.   

Our soil is naturally 7-8.   Someone brought in tons and tons of crushed lava rock and sand forfill and  ground cover since the house was built in the mid 80's.  

Soil under the rock was recently tested by a commercial lab at between 5.5 and 6.5.

The berries love it.  The figs (before I ammended with lime), not so much.

The problem with pine bark is that the bacteria in the wood eats up most of the nitrogen in your soil in the process of breaking down the wood, And pine can also get very aciidc as it breaks down. 
So, instead of pine bark, I use Cypress mulch, it's small and shreaded, allowing for water, and air passage. Breaks down at a much slower pace, so less Nitrogen is robbed from the soil, and doesn't become acidic in the soil.

I use builders sand which is very course, and very gritty. Playsand is too fine
And I also use lava rock. I buy the Bar-B-Q type rocks, and break them up to the size I want with a hammer, it's a good source of iron and trace minerals for your plants and it lightens up your soil with more air spaces for the roots.

For calcium, I use finely crushed up Tums, It's Calcium Carbonate also!
and can be mixed in the soil, or watered in since it desolves readily in water.

Dan...

Thanks for the "bark" tip.  Never would've thought about the Tums.  I have some old "Centrum, Multi-Vitamins" that I found in the medicine chest, and I throw a tablet into a 5-gallon bucket, wait for it to dissolve, and water my trees with the "tea".  It probably doesn't work, but it makes me feel better, and the figs aren't suffering. : ) There minerals in the tabs, and maybe it helps the trees...who knows?

Frank

Dr Al has written a lot about Lava rock and coral.  It's in the container growing section of Garden Web I think.  I think he said the lava rock was too big and maybe it powdered too easily, not sure on that last point.  Concerns over sodium were expressed for oyster shells by someone, not sure who.

rcantor...

Thanks for the useful information...I didn't think to check that forum.  I got some searchin' to do.


Bye!

Frank

Crushed coral will add very little to no salts to the soil mix. If one wants to "ensure" there are no salts or other chemicals soak the crushed coral for a week and replace the water once a day. 

FOr myself I have a ready supply of excess coral as I used to aquaculture various corals. The best medium to grow coral on is in fact dead corals. I have been using the remains since as soil amending agents in the outside garden as well as in pots. Last for a few years then degrades into the over all soil just as lime pellets do. 

Yes, coral is one of the main base materials for limestone/dolomite.


Chris
Geology and Environmental Engineer  

Chris...

Thank-you very much for your comments, and adding additional, useful information.

I was a little concerned about the salt content, and your soaking, and leaching suggestion settles the questions.

Thanks, again.

Frank

In my previous life I was involved with the use of Polyethylene pellets.  I have recently found bean bags at a local Goodwill and was able to get them for 2 dollars each.  I use the "beans" (high density Polyethylene resin pellets) as a substitute for perlite.  It is inert and a real good recycling effort.  They are very easy to re-use, float them out of your mix.


Thx
Danny K
Marshall Tx