I've been collecting aroids for less than a year, but with over 50 in my room already I was having trouble with under/overwatering. Some plants had much heavier soil than others and dried out much more slowly. So I went looking for a light potting mix, but I couldn't find a good mix in stores. I made a huge spreadsheet of recommended aroid potting mix recipes, trying to find the perfect mix. I couldn't find some ingredient locally, but in my search for alternatives I came across a bonsai forum where they recommended moler clay.

Moler clay (terramol) is a calcined clay product that is light and has a high moisture retention capacity. It's porous, drains well and allows oxygen to the roots even when saturated with water. Where I live it's sold as kitty litter and it's really cheap (don't put your plants in just any kitty litter - most types will kill your plants).

I repotted most of my aroids into moler clay. I removed just about all the soil off the roots - this was scary - and then put them in pots with just the moler clay (and a small layer of vulcanic rock at the bottom so the tiny medium didn't pour out the bottom holes). Afterwards I flushed the potted plants until the water coming out the bottom was no longer red from the clay dust. I was scared that taking all the soil off the roots would cause at least a few leaves to die off, but none of the plants showed any signs of stress and the drama queen Spathiphyllum didn't even droop its leaves. It's now two months later and all of them have continued growing like nothing happened. Yay!



Pros of moler clay:
- Water as often as you like
- Root aeration even when wet
- Some wicking action - you can water from below by keeping the bottom of the pot in water
- Changes colour when it dries out, so you can see when you need to water again
- Increases local humidity
- No more fungus gnats
- Cheap

Cons of moler clay:
- Made of specific Danish clay, so only available in Europe
- Mostly untested
- Low cation exchange capacity - it doesn't hold much fertiliser by itself so you need to always add a little bit to your water
- Always moist, so it's prone to algae and may cause rot if leaves touch the medium
- If you don't mix it with other ingredients, it dries out completely in 3-7 days

Anyway, on to the experiment part. So far all the aroids I put in moler clay already had roots. I tried some cuttings that had rooted in either water or Sphagnum moss, and they did fine after being transferred to moler clay. But I haven't tried putting cuttings without roots into the medium directly. I took 22 pothos cuttings (14x Epipremnum aureum, 12x Epipremnum pinnatum). I put half in Sphagnum moss and half in moler clay, all in clear cups with a drainage hole at the bottom. You can see the difference in colour of the clay dry vs wet.



I'll update in a while to show the progress.

Your plants look amazing, very happy and healthy! It sure loooks like the moler clay was the perfect solution for you! I'll look forward to seeing your updates on the cuttings and how they progress!

Very interesting.

I have used a variety of this product for years. We always called it Aliflor. Some people buy itunderthe trade name Leca. It is a big part of hydroponic growing and some orchidists use it to grow 'semi-hydro'. I use it as the false bottom layer in my terrariums, and also mix it into the potting mix for terrestrial anthuriums and philodendrons. I have a lithophytic anthurium (Anthurium reflexinervium) that grows totally soil-less in Aliflor and Lava rock chunks

I had forgotten about Aliflor. I used it on some orchids for a few years and it worked ok. If you ever needed to repot for some reason the roots were very firmly attached and almost impossible to remove from the round balls. Seems like I mainly used it on phals and cattleyas but I don't remember why. At that point I was growing mostly phals in sphagnum moss and I was looking for something less time intensive I think. I really had good luck with the moss but repotting every six to twelve months for several hundred phals was too much.

It's been over half a year, time for an update. I've neglected the Epipremnum cuttings. They've had little light and I watered them maybe only once a month. I think I've added fertiliser to the water just one time. I'm honestly surprised that almost all of them survived and grew new leaves. Anyway, here's a comparison between August and now:


Epipremnum aureum, moler clay vs Sphagnum moss:

The ones on moler clay did well, but most of the ones on Sphagnum moss are a little larger. One of the Sphagnum ones managed to get a root onto the bottom so it got all the condensation water and grew much bigger than the rest. However, a Sphagnum ones didn't make it and another one looks like it maybe won't make it either.

Epipremnum pinnatum, moler clay vs Sphagnum moss:

One of the Sphagnum ones managed to put a root into the moler clay of another cutting and I didn't want to separate them, so it's just one picture. All of them did well.

Simple data analysis, error bars show min/max:

Cuttings on moler clay had a better survival rate and were more uniform. Cuttings on Spagnum moss on average grew more leaves and longer shoots. I think this is because of the way I treated them, and not inherent to the medium. The lower survival rate could be due to underwatering, combined with a lower water retention of Sphagnum compared to moler clay. The increased growth on Sphagnum moss could be due to not using enough fertiliser, combined with Sphagnum containing some nutrients whereas moler clay is essentially inert.

Conclusion: both Sphagnum moss and moler clay are OK for cuttings even if you neglect them. If you use moler clay for your cuttings, use some fertiliser in your water occasionally. If you use Sphagnum moss, make sure it doesn't dry out for too long.

Excellent!

Thanks so much for sharing. This post was very interesting and informative. I may have to give it a try.

I use the clay balls in the bottom of my terrariums for the water reservoir. My largest tank, #75 is where I have my Alocasia cuprous and ALocasia infernalis. Both are thriving, they have sent roots down through the fir bark, cocohusk, charcoal and perlite top dressing into eh water reservoir where they have spread out hugely. They are basically growing almost in semi-hydro. I was not sure a Jewel ALocasia like Cuprea would make it like this, in fact, another terrarium enthusiasts told me it would rot. But it just keeps growing, and has made an offset which I harvested

I think it's time for an update on the moler clay!

Today I noticed my Homalomena was trying to attach itself to the felt it was on.

So I decided to repot it and uhm.. I probably should've done that a bit sooner.

I bought and repotted this one last August, it was less than half its current size. I guess it's happy?

Repotting a plant in moler clay is really easy. I just put it on top of a layer of fresh stuff, fill it up, that's it.


I'm quite happy with this growing medium. I bottom water my plants on a layer of felt that I always keep wet, and I don't have to worry about overwatering or underwatering. I even have a Zamioculcas constantly wet with this stuff and it seems to be doing fine. I use plastic pots for the small plants but for the biggest ones I need to use terracotta, as the medium only wicks about 20cm on its own and then a clay pot helps pull up water to the top.

Currently I put most of my cuttings in Sphagnum, but it's not easy to get that off the roots for repotting. So I started another propagation experiment. This time I'm testing pothos in 8 different media. From left to right: leca, moler clay, volcanic rock, pine bark, coco chips, aroid mix, Sphagnum, water. Let's see what happens

The aroid mix is the one I also use for my big Monstera deliciosa. It's equal parts moler clay, pine bark, coco peat and coco chips.


I'm contemplating whether I should put my big bird's nest Anthurium in moler clay, or a mix similar to the one above. It's still in the awful potting soil that I got it in last January, I haven't found the courage to repot it yet. It currently has a really weird fasciated inflorescence.


How well does a bird's nest Anthurium cope with repotting stress?

Most of them are pretty forgiving if you don;t do anything like actively wash the soil off the roots.
This is a great experiment by the way! I am experimenting with Keiki paste. Have you used it?

Thanks! I do actually try to get all the soil off the roots when I repot from soil to moler clay, but I do that when the soil's dry so it comes off easily. If I recall correctly so far only two of the plants I repotted this way dropped leaves right after repotting: a Syngonium erythrophyllum that I was too rough on and a very sad Anthurium that I rinsed to get rid of bugs.

Keiki paste sounds nice, any results so far? It's the same hormones that are produced when you take a cutting, right?

Gina1960 said:I use the clay balls in the bottom of my terrariums for the water reservoir. My largest tank, #75 is where I have my Alocasia cuprous and ALocasia infernalis. Both are thriving, they have sent roots down through the fir bark, cocohusk, charcoal and perlite top dressing into eh water reservoir where they have spread out hugely. They are basically growing almost in semi-hydro. I was not sure a Jewel ALocasia like Cuprea would make it like this, in fact, another terrarium enthusiasts told me it would rot. But it just keeps growing, and has made an offset which I harvested

That's really interesting that the roots seek it. I don't see why semi-hydro shouldn't work. My baby Cuprea and Dragon Scale are both doing well in moler clay, constantly wet from bottom watering. My lauterbachiana put out three inflorescences and a new leaf at the same time, I should probably check if it's as rootbound as the Homalomena was.

Even my Colocasia has come back from the dead, although now I'm worried it might have mosaic virus. Edit: here's a closeup, is this healthy?

My ALocasia cuprea and ALocasia infernalis are in my terrarium in basically semi-hydro. The terrarium is constructed so that the bomb 2-3 " is filled with molar clay, then a screen over that and a top planting substrate of lots of orchid bark, coco husk, etc. The plants roots systems go all the way through the screen into the clay, which is a water reservoir for a waterfall feature so it is constantly circulating and constantly replenished as it evaporates. They are VERY happy!

Still haven't repotted the big Anthurium but the propagation experiment is going alright. Almost all the Epipremnum cuttings are already growing some roots after two weeks. Most roots to least, from left to right: Sphagnum, terramol, volcanic rock, leca, water, my aroid mix, coco husk chunks, bark chips:

I did have to wipe all the leaves off because most had some superficial mould, I guess I should air the propagation box a little more frequently.

I love this thread and these experiments... now I feel like trying an experiment of some kind!

I am trying to use leca as much as I can but am mostly using it for my hoyas and with a water reservoir underneath. I would love to try the medium you've found if it were in the states, as I'm keen to try something more granular like lechuza pin - which always seems sold out.

I'm curious if I could but someone in leca without keeping the bottom in water, or if it would get too dry. Even when I root my hoyas in leca I think I do it in a funny way, since I often fill a lot of the leca with water... but sometimes I am more daring when rooting and will only have water on the bottom. As someone else mentioned I've also noticed that even if I root them in water with some leca to stabilize them, they do seem very attached to their leca... I assume it'll have to come with them when they reach their final potted destinations. However, I do find hoyas hard enough to water properly that this seems like a safer way to keep them (in leca)

I have never considered moving any of my aroids to a medium like this, but it would be a bit of a relief if they would be happy in something of the sort. Perhaps deep down in my heart I'm just a 100% hydro gal. That's a little bit of a set it and forget it situation.

I also must give a kuddos to the enterprising pothos - the one who found the water below, as well as the one who attached to the kitty litter.

I'd also love to see Ginas water feature, lol.

I guess I almost love roots as much as I love leaves!

Have you tried semi-hydro with a wick before? That may be something for you. I saw some posts by "melelina_cattleya" on Instagram that really inspired me. She uses leca (sometimes also seramis) in nursery pots with a wick coming out the bottom, and then the outer pot acts as a water reservoir. The water is slowly sucked up via the wick, keeping the leca evenly moist until the reservoir runs out, while the roots never touch the water directly. The wick is just a fluffy polyester baby blanket yarn. I'm currently trying it with some Monstera adansonii cuttings.

Four week update on the propagation experiment! All media have at least one cutting that took. Water, terramol and aroid mix seem to be doing best, as well as one of the cuttings in Sphagnum. Shoots are forming with the water cuttings, one of the Sphagnum cuttings and they're starting to form on both the terramol cuttings, no sign on the other ones yet. Only the terramol cuttings have nice forked roots.

Left to right: Spaghnum, terramol, water, volcanic rock, bark chips, leca, aroid mix, coco chunks.

8 week update and end of the experiment!




- Moler clay did well, even better than Sphagnum moss this time
- Water propagation worked well too, with longer but slightly less forked roots. The cuttings on water were the first to push out new leaves, too
- Leca is not great for propagating, almost no roots grew. Might work better if the leca is smaller (I used ~15mm)
- One out of two cuttings in lava rock did surprisingly well with a nicely forked root. Might work better if the media was a little smaller (I used ~15mm)
- Aroid mix and orchid bark work ok but are a little slow and not ideal for hydro
- Coco husk chips did not work at all

I repotted the big Anthurium and it took well. It dropped its smallest oldest leaf but other than that it looks very healthy. All the other plants are doing well, but I do see some signs of nutrient deficiency especially in the Rhaphidophora tetrasperma and some Philodendrons. Might just be nitrogen since it's only the fast growers, but could be trace elements. I'm currently using pretty cheap fertiliser so I'll see if I can find something better. I've also been thinking about making my own nutrient solution, maybe with worm tea or even going anthroponics.

I bought a sieves set, so I can grade my hydroponic media to the same size. I really like sieving, it's so relaxing. I only have pumice, leca and moler clay for now but I'm thinking of getting perlite, smaller lava rock, Lechuza Pon or Vulkastrat etc. to play with. Anyway, on to the next hydroponic media experiments!

Experiment 3: media comparison, all small grade (sieved 2-5mm). I'm testing moler clay, pumice and micro leca, as well as a 1:1 moler/pumice mix and a 1:1:1 moler/pumice/leca mix. Plants are Philodendron hederaceum, already rooted cuttings. This time I'm using a wick into a nutrient water reservoir.


Experiment 4: media size comparison. I'm testing a DIY hydroponic media mix in three different sizes: 2-5mm sieved, 5-7mm sieved and 7-12mm sieved. The mix is roughly 50% moler clay, 30% pumice, 20% leca. The plants are the 6 Epipremnum aureum from experiment 2 that had the best roots. These pots will be in my constant bottom watering system.

Interesting results from experiment 3. This was the small grade media (sieved 2-5mm) test in a wicking setup. This has been the most care-free experiment for me so far, because it's self watering with a reservoir that lasts months. I literally didn't touch these cuttings for 3 months.




From left to right:
- 100% micro leca: hardly did anything
- 100% pumice: best root growth, nice root branching, best leaf growth too
- 50% pumice, 50% terramol: nice roots, nice leaf growth
- 33% pumice, 33% terramol, 33% leca: nice roots, nice leaf growth but less than the 50/50.
- 100% terramol: nice roots, nice leaf growth, similar or slightly worse than the 50/50

Of course single cuttings don't produce statistically significant results, but it looks like pumice is the best media for propagation out of these three. Terramol is also decent, but again leca didn't do much. Too bad pumice is so much more expensive and hard to get here.. The 33% and the 100% terramol both have a second growth point coming, not sure what that says about the media.

During this experiment I also put some random Epipremnum aureum cuttings in even smaller pumice (sieved 1-2mm), also with a wick. Those absolutely exploded, and they weren't even in my propagation box, so for the next experiment I will also try that even smaller grade.