Using Lava rock as a growing media?

homehydroFebruary 12, 2012

This thread is created, and only for people who have used Lava rock as a growing media, wish to use Lava rock as a growing media, or are interested in using Lava rock as a growing media. No other replays will be tolerated. Any reference to hydroponic systems or anything other growing media other than Lava rock will be dealt with harshly. That's simply to make sure the thread does not GET SIDETRACKED, AND/OR BECOME OFF TOPIC.

Anyone else use Lava rock as growing media before?

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It tends to be a bit more expenisive then hydro-tone. But that could be a regional thing.

    Bookmark   February 12, 2012 at 1:02PM
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Around here lava rock is dirt cheap and abundant, but it doesn't lend itself to small net pots.

    Bookmark   February 12, 2012 at 10:01PM
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It's my understanding that lava rock needs to be washed thoroughly. I am wondering if anyone has had problems with pH using it.

Do you only grow in small pots? If so why? Don't you grow any large plants?

    Bookmark   February 26, 2012 at 6:32AM
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When I use net pots, I only use small ones. I haven't found a vegetable yet that requires more then a 2" net pot(I suspect corn might and possibly brussel sprouts). I can't speak to large multi-year plants but basically anything with a stalk 1/2" or so doesn't need a large pot. I tend to plant trees and berry bushes in the ground because I know at some point I'll be negligent of them. Oh! when using pots I've only used NFT and DWC.
When I was growing the soy beans in EnF, I didn't use pots. In that case I did use lava rocks to fill the tray. I didn't really have any pH problems, but then the whole deer incident kept me from having a complete "season". They did a tremendous job of retaining moisture. I suspect, in that system, I could have watered them once a day and they'd have been fine, but it was a wet season that year.

    Bookmark   February 26, 2012 at 8:32PM
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I have grown many (if not all my) tomato plants with stalks well over 1/2 inch wide. When talking about using 2 inch baskets, one thing that is extremely important (and makes a huge difference) is the type of system you are growing it in. In a DWC (Deep Water Culture) slang for "Water Culture" the roots have more root space than 2 square inches. Thus, it can be confusing for those that don't know how the type of system used will affect the plants growth/root system. Fact is if you have the right plant support, you don't need to use any baskets at all. In any hydroponic system, as well as if the water delivery system is run correctly, and the plant support system is designed right as well. But saying it dosen't need any root space at all (even just 2 inches) is untrue (same for saying the the smallest basket) in most contexts.

    Bookmark   March 1, 2012 at 7:05AM
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I have used it before in a DWC setup with 8 inch net pots (5 gal buckets). This was an attempt at an organic set up..of sorts. The surface area of the lava rock would help provide an environment for beneficial bacteria to grow.

Overall it worked well. Very hard to clean though, haunted by the red dust. Extremely hard to clean roots of off. My powerwasher just creates more red dust.

I recommend the pebbles over the larger rocks.

    Bookmark   March 2, 2012 at 2:45AM
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I know you mentioned that you use NFT and DWC systems, and that you were referring to those as your experience with regards to pot size. I probably would re-phrase my statement/reply, but cant edit the post. So I'll explain my thinking more here. For every post there are thousands of people that read them that aren't registered in the forum or even reply. 99% of them don't read many of the other threads (your past statements), thus don't understand the details that would make a difference. In that context I wanted to explain/clarify more that it depends a lot on the type of system used, how it was built, and how it functions and their specif growing conditions that make the biggest difference. Rather than just picking a size, and hoping it works for you because it works for someone else. I always prefer getting people to think about their system/system design, and the pro's and con's of it rather than just giving specific (do this) directions.

"I have used it before in a DWC setup with 8 inch net pots (5 gal buckets). This was an attempt at an organic set up..of sorts. The surface area of the lava rock would help provide an environment for beneficial bacteria to grow. "

This is a great example of why I try to give pro's and con's, rather than specific (do this) directions. Even though you were utilizing the same type of system (DWC), because you were using organic methods, the larger amount of growing media served a valued purpose. That holds true for any system design (organic or not). It depends on the specifics of each persons situation, system, system design, environment, and even expectations.

Did you have any pH issues using the lava rock?
Specifically, pH issues in regards to the buildup of rock dust in the system while in use?
Did you let everything completely dry out, then try and sift the dead plant roots from the lava rock before washing it out?
If you used a EC/PPM/TDS meter did you notice a increase as the lava rock dust built up in the system?

    Bookmark   March 2, 2012 at 6:50AM
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I'm just sharing an experience I have had, I am by no means an expert.

This was about five years ago, and indoors. The red dust would tend to settle on the bottom of the buckets after some time. I do not remember ph problems. Can't really comment on the tds, as I never checked.

This is a first lady tomato clone about 2 weeks in. 8 inch pot, 1000 watts.

I have several bags of the pebbles I will be using once springs rolls around for some pepper plants, outside ebb$flow.

About cleaning, I accidentally let the roots rot in the rocks. It was some nasty stuff.

    Bookmark   March 3, 2012 at 2:02AM
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Type of system is not actually important so much as available space for roots. you're correct, HH, in that no base support is required. I use 2" pots for support of smaller plants. a small pepper plant won't require any more support where as a tomato will but only as it gets larger.
I never stated that all the roots would stay in the basket and knowing they won't is why you don't need anything larger.
It is not my job to ensure everybody knows everything about growing plants (I don't know it all myself) If anybody is fool enough to read one post and act on it, well . . .
a fool is as he does. It's not my job to ensure the world is without fools. Thats an unsurmountable task. Only a fool can remove his title. All that means is I respect people enough not to assume they're fools and unable to think for themselves. That's why my responses don't imply ignorance of the subject.

    Bookmark   March 5, 2012 at 9:48AM
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muslickz(Zone 9 CenFL)

I have never used Lava-Rock as a medium before, But I have filled my whole ebb and flow table this year with it. Got a super deal on some so why not? As far as PH.. Well I started with 6.1 and after 48hrs it went to 6.3 so not too bad at all.

Though the rock I am using is LARGE I am hoping it will work out, but with what I paid for it it would be an easy replacement if not.

Was going to use hydroton but at $300 to fill the bed VS $30 to fill the bed with lava it was WAY cheaper to use lava.

I'll post a follow up in a month or so and let ya know how it works out.


    Bookmark   February 8, 2013 at 11:57AM
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You might want to cover the top with something or else algea will start to grow near the moisture line, Well, unless they rock is substantially deeper than the water level is high.

    Bookmark   February 8, 2013 at 1:18PM
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I've used both red and black lava in a home made DWC setup utilizing 18oz. plastic drinking cups drilled full of 3/8" holes for pots. I did have to modify some lids to fit as Grizzman sugests, but that was mostly due to evaporation loss problems. Algea & Ph didn't seem to be any more or less of an issue than other inert mediums such as pebbles, gravel or perlite. I did clean the lava between uses in a pressure cooker to remove dead root matter. It does create a gritty dust sedement in the bottom of reservoirs which may not be acceptable in many systems. However, it is very porous and roots cling to it quite well.

    Bookmark   February 24, 2013 at 5:22PM
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Lava rock is fine as long as you don't move the net pot full of it very much. The sharp edges can crush a stem much more easily than hydroton. Also, if your system is making a vibration from the pump, the sharp lava rock can cut the stem. Otherwise, it's fine. Any ph-neutral rock will work.

    Bookmark   February 24, 2013 at 6:54PM
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why not just use gravel like some do?
its the cheapest by far

    Bookmark   February 24, 2013 at 8:45PM
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Gravel is also very heavy.
That is why I don't use it.
Well and I have a bag of hydroton laying about.

    Bookmark   February 24, 2013 at 9:06PM
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Yes Cole,
Lava is very sharp and it may "wound" roots if vibrated or moved around a bunch. However most roots have a tendency to heal and branch out. If you've ever pruned roots you have experienced this first hand. Maybe dead root matter can cause Ph problems in some systems although I've never seen lava cut plants off at the stem.
Yes Grizzman,
Gravel is very heavy and not very porous.
Lava is very light when dry and some pieces have a tendency to float untill soaked.
Hydroton Is most probably a better medium.
Lava in my neck of the woods is a good cheap medium.
The only medium cheaper would be Red Hard Clay.
Good Luck,

    Bookmark   February 26, 2013 at 10:57AM
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I really rigged a homemade lava rock hydroponic "tank". I took a plastic bin cut to about 6-8" tall, set a seed rack upside down to set Plastic baggies with slits I put in them to hold the lava rock and plants. Just the bottom o the baggie was in water and wool felt for a wick inside the baggie. I rinsed the lava rock first to get the dust off before planting and have no idea what the pH was. I told you this was crude at best but works great.

    Bookmark   April 5, 2013 at 4:04PM
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I think it is safe to assume that not all lava rock is the same. Certainly not all volcanic rock is the same even. So to clarify, this discussion is specifically about lava rock aka scoria, not perlite, pumice, azomite, akadama or anything else. I read a thread where somebody did an in depth comparison using a number of soil amendments and their properties in terms of water retention, porosity, and things like that. When it came to perlite, pumice, and scoria, the study concluded that similarly sized particles will yield such similar drainage properties as to be nearly interchangeable.

However, I don't recall if the thread distinguished between red and black lava rock, and I am very curious as to where most lava rock in the States comes from, since I am assuming it comes from more than one location, and if anybody has any info on this or other info on the difference between red and black lava rock, it'd be greatly appreciated. For instance, how do they affect the pH of a soil mix, and how does the structural integrity compare, things like that. I'm also curious as to what sort of affect the different types of lava rock have on gH when kept in water, since this thread is under hydroponics after all.

I am really not sure what this thread is asking -- is it okay to use lava rock? yes.... -- other than that though, not sure... especially given that the topic of soil amendments has been discussed in great detail by more knowledgeable and experienced gardeners than myself, I will just say that for those who have yet to hear or make the switch, there is a great new group of products that I would like to suggest trying. These are the expanded recycled glass aggregates, or as I first stumbled upon them, Growstones. I know there is at least one brand which markets a similar product for use as a hydroton replacement in dart frog vivaria and such, where it is used a substrate to construct a false-bottom. The main horticultural brand, or Growstones comes in 3 sizes. Make sure you get the right one! Large is larger than hydroton, though the pieces are irregularly shaped so some are larger than others. Medium is like large perlite, and the small is also called Gnat Nix since it is tiny and apparently capable of stopping fungus gnats by mulching your containers with 3" of the stuff.

Besides being made from recycled glass, (unlike perlite, which may be organic, but is still mined from the surface of the earth), it also has other benefits, such as a higher water and air holding capacity, and a much higher surface area, I believe that it's actually 70% more porous than perlite, (giving beneficial microbes that much more area to colonize!), not to mention it holds its (uneven) shape better! It can also be re-used, making it a prime choice for hydroponic systems.

    Bookmark   February 12, 2014 at 2:28AM
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I have used lava rock for years, and found it an excellent growing medium, the weight is considerable if using an ebb and flow system but hold the nutrients longer than straight expanded clay. I am using expanded clay plus a small proportion of lava rock which holds a little more moisture.
I have found over a period of time the lava rock breaks down a little and when flushed leaves a rusty coloured sediment which is easy to flush clean.
As the lava rock is more porous it is a very good substitute other than using vermiculite or perlite which does break down and condenses. After 40 years of hydroponics where I have used every medium known to man ( only kidding) the lava rock mixture in the ebb and flow system works . I have not tried in pots in a drip system , however I feel the float method I think would be like the peverbial lead balloon, and would be too heavy to support the lava rock.

    Bookmark   February 13, 2014 at 5:15AM
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I grow 60 5 gal buckets of tomatoes in a DWC recirculating system.6in net pots with lava rock. The lava rock is an essential part of this systems success. Provides beneficial bacteria culture which hooks the plants up with nutrients and wards off bad bacteria.Basically the same processes that occur in organic soil are taking place in this hydro system. This is a living organic system as opposed to many other hydro systems which are sterile. Peace and happy growing.

    Bookmark   February 18, 2014 at 10:17PM
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I was recently in Arizona and kept seeing this stuff on the ground that looked like a cross between lava rock and Hydroton. When I asked what it was it turned out to be the stuff the state throws down on the highways for traction if there is snow. Apparently it is volcanic cinder from a couple ancient volcanoes near Flagstaff.

I would very much like to buy this stuff, the sizes and shapes are exactly like you would get in hydroton. If they throw it all over the roads it would probably be much cheaper than hydroton even if I had to soak it or wash it.

Has anyone else come across this stuff? is anyone selling it?

    Bookmark   March 3, 2014 at 10:31AM
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hello this forum mayb closed i am looking for only natural and organic growing mediums, i have used lava rock on and of since about 1983, the first time i used it right as it came from the bag that lasted till about 88, i got some free time on my hands and i pulverized my lava it was about 2 - 5 gal buckets worth when i gave up i still have that batch i just rinse it well if i want to use it i have had real good luck just using it as a normal water as needed medium, our thinking was such great things come from the islands and had seen the great flowers there , pinapples come from there so,,, why not grow in it as long as i keep it well drained and no obstructions on the drain holes it has been some good medium, but i never really had much time to actualy set up a real hydroponics system like u see now days it was just ur bare knuckles pump the water in and cover the medium and drain it out well, since then i have been tryn to utilize some water and slopes and grow fish and plants in our ponds and i have ignored lava rock till the last few yrs but now i am really looking into growing only organic in truly only organic containers and anything touching the water and its been very tricky since my wife does cancer treatments and my background is environmental i have looked at cancers and sickness as a result of what we eat and whats in all of what we digest and the containers that touch it and what its grown in and watered with,,, so,, my point? i have used lava rock but consider it somewhat inert but with my chemistry background and knowing whats in all the water and whats gonna be in the fish excretions from gills and excrement's it will have some affect on anything in lava rock that might dissolve up to the point my fish algae coats it with that slim, so my concern? i saw one blog where the blogger says lava rock gives off dangerous chemicals ,,, but its blog to me seemed to b pushing claycorn ,,yet its man made from who knows what and is imported from china i also see that it starts out and may stay with a p h of 8 my lava rock in and 7 ph filtered tap thru 3 charcoal filters shows 8 depending on whose eyes u use, ,,i see where the most fertile lands on earth are in volcanic soil but upon checking cancer rates in these areas i find that many say they have high thyroid cancers in those areas of course the people are exposed to more than the soil yet i found a very few isolated volcanic areas where no cancer existed but they say its from the general diet high in certain elements,, since lava rock numbers i have seen imply 66% silica, 16% aluminum. 10% iron,, lists only 10 total elements i am wondering if i should be concerned with the aluminum, and its possible affects on humans causing dementia, n Alzheimer and no i do not want to hear its a metal and it will not react i am talking pure submersion in my fish ponds and in my grow beds ,, i have stayed with what i think is river rock for now since thats what i ve always used for fish, (and its probly all conglomerate of marble (igneous limestone), granite, quartz, limestone, with one pebble or 2 or lava rock) but since i am planning on eating the fish and i am tryn to remove all man made items such as plastics, vinyls, pond liners, additives in my fish food and meds and hormones not used and all fish treatments removed ( if they die they get blended for chum), are there any other obsessive people who can give me any reason to not use lava rock over man made clay balls for grow medium my brother n law is sure that the clay balls have been developed by the professionals, my son who is helping with the learning is too young to do anything except as what the hell are ur talking about old man? i have not finalized my choices but i see the professionals as only there to part me with my money and sell me some snake oil when it comes to clay made pellets, ,, so do i have to worry about the aluminum, or any of the other 7 items aside from the silica i know i should not breath when i pound it to a pulp, i am tryn to be as true and pure organic as can knownly be and growing inside greenhouses and enclosed ponds not sure how i m gonna get the birth control pills outs the water if its not truly well water but has been slipped in from the lake if my charcoal filters won t remove it except to maybe us my springs that have p h of 6 and drill my own well, of course when i add the wrong things to drop the ph it actually draws out more of my alkalies but i have probly always grown my crops in a ten due to growing in this east texas iron ore and sand , and in central texas dirt and here i have always added gypsum to cancel out the chlorine added to the tap water if you can sort this out and it gets past censors please let me no if anyone out there can shed some lite on my determination to use all lava rock and river rock and white marble or limestone rock

    Bookmark   March 5, 2014 at 3:42AM
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Expanded clay and Scoria is a tried and tested method giving very good results.
I have changed from a flood and drain to drip system with these 5 containers , which prevents over watering and easier to control. These tomato seedlings are Heritage Arkansas which I am trying for the first time they were grown from seed and are two weeks old.
I am using part A and Part B dry mixture which I make up into 2x11 litre containers with taps for easy use to add when required ..

    Bookmark   March 6, 2014 at 2:34AM
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Has anyone used these lava rocks from HardScapes by Quikrete?

    Bookmark   July 3, 2014 at 3:47AM
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Those look like what I use but not sure about the brand. I got them at lowe's years ago.
It doesn't work well in 2" net pots as the individual rocks tend to be too large but for larger pots or an EnF bed they work excellently.

    Bookmark   July 8, 2014 at 10:35AM
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Thanks. I'll give them a try

    Bookmark   July 8, 2014 at 6:02PM
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