Cultivation on exterior of porous ceramics

I'm experimenting on growing moss and orchids on the outside of unglazed terra-cotta.

For this, I am hand-throwing and baking my own custom pots in a nearby ceramic studio. It is not so common for a grower to be able to shape ceramics in any way so lets abuse this to experiment.

This thread is to document and share my major insights, and allow other growers to share ideas, experiences, suggestions, tips and enthausiasm.

This post has some inspiration and sources. The next posts will focus more on my work.
Moss cultivation on pots

Make DIY Moss Covered Pots With Living Paint
Посадка и пересадка орхидей © Inna Liapin

Some pots designed for exterial orchid mounting are available

Buy Orchds online now - Roellke Orchideen and
Terracotta Mounting Jars

The most complete source on guides tips and experiences is the following:
https://orchideria.com/mounting-orchids-on-clay-pots/
The author collected various related sources and images shown on the following pinterest page
20 Mounting Orchids on Clay or Terracotta ideas in 2021 | growing orchids, orchids, clay pots
This guide is in german
Aufbinden auf Tonröhren

Some more illustrations and sources:
Nanovivarium
Nanoviv 080804
Посадка и пересадка орхидей © Inna Liapin (russian?)
How to Use Olla Irrigation (the method used is similar to the olla irrigation method, just not underground. If you are looking to buy similar jugs for mounting the searchterm olla might give you additional leads)
terraplanter - visibly follow the journey from seed to plant ( a facebook-clickbait-level kickstarter )

 

I made a first batch of pots of various sizes and shapes, most of which were designed to be hanging. Some guide suggested that orchids would have a better chance of survival if there was an existing biological culture on the pot already, thus it was recommended to grow orchids together with mosses. Here are some pictures from 3 weeks ago.


Jugs are filled up with water. A mixture of four different wild mosses in my area have been mixed with yoghurt to a weird smoothy and smeared on the surface to seed mosses. The yoghurt was said to have a good ph and it helped making it stick to the surface.
I chose four different mosses growing on the ground and on trees. We will find out which spieces respond well, or if we get a mixture.
There were some more pots, but the nicest one was the one above on the right. The thick layer of moss on top was just put on there to see what that would do. Moss on top does not really seem to root at this point, but my main goal was to get the seeds sprouted anyway. I might discard the loose pieces at some point, but now they give it a nice look instead besides a moldy smoothy structure.

Now; about 3 weeks later - the same pot that was earlier shown on the right;
Moss is noticably growing. I tried to mount two orchids already, as I was a bit impatient and wanted to learn how they would do on there. They didnt change noticably in this timeframe, so I cannot say anything about that. Here's some pictures



These pictures are from the largest pot ( ball shaped, diameter ~ 17cm), and growth is alot quicker on this one. I'd guess this one has a 6 to 7mm wall thickness. Water level drops about 1-3cm per day due to evaporation. Pots are cold and damp on the outside. Sometimes the outside is shiny from the moisture, but not always. Maybe due to varying air heat/moisture from day/night sequence. They dont drip water on the floor.

Im estimating that:
- higher pots will have more water pressure, increasing moisture.
- Thinner walls will lower resistance of water flow through the surface, increasing moisture.
- Shorter ceramic baking times increase porousness and thus waterflow and moisture. Now they are being baked at the studio's default bisque-bake settings. I could let them be fired to a higher temperature, making the pots stronger and less porous.

Furthermore I like the round jug like shapes compared to cylinders, stylewise and because the ratio between water capacity and surface is higher, requiring less frequent checkups. Cylinders offer a lot more vertical surface for plants to grow on though.

I'm giving normal tap water. ph is about 7.5. Sometimes I spray the plats with a slightly more sour mixture (ph~6) made with citric acid, as I heard most plants need a slightly sour environment. I'm thinking about what would be the best plan for watering, as the substrate does not get flushed or anything, and salt accumulation is a danger with all the evaporation. I worry that this will be an issue at some point, but do not have ideas to check this besides plants dying because 'something is wrong'. Would my tap water be okay for watering or do i need to use distilled water? How much fertilizer should I spray on, since nutrients are not flushed away?

TLDR: Moss is growing. Tips? Ideas?

 

For moisture throughput I intend to keep clay mixture and firing constant, while varying wall-thickness throughout experiments and do trial and error.

If salination is really a challenge in this unconventional setup, as ions enter the system but only the H2O molecules evaporate, wouldn't it make sense to water with as little nutrients as possible. As once nutrients enter the pot they will always eventually end up on the outside surface, instead of being flushed away by rain or watering.

My tapwater contains (average of monthly measurements of supplier. They had the data available for me, which is nice):

Nutrient [ppm]
HCO3 120
Cl 55
SO4 48
Na 38
Ca 45
Mg 7,3
NO3 9,6
Fe 2,6
Al <3,0
F 0,22

Ph is stable at average of 7.95

Seeing these numbers the majority of salt buildup will be limestone-ish, but the concentrations are indeed much higher than 25ppm in total.
I had to google "RO water" but I see that it is reverse osmosis to desalinate.
How much did you spend on such a device, and how was your growing experience while using your technique?

 

Ray, your website is pretty awesome.

Seeing how in depth you went into growing and your experience, I am doubtful about my question about your desalinator. You probably had a higher budget than I now have . I'm a student growing from a windowside. Anyhow, that might not be the biggest problem.

Reading various things from your website, I came to realize i'm more like the orchid murderer from the article on your website "No longer a killer", besides the fact that I'm still murdering. I already see that I made various mistakes while attempting to mount newly bought orchids on my experiments, such as the fact that they dont show fresh root growth. I killed all my previous orchids besides two spieces of dendrobium in the past 10 years, yet now I'm buying more plants of which I have no idea how to grow. These poor plants ought to be afraid.

I was hoping to create environments that would let me grow in my windowside, as I am living in a small student appartment. This project was aimed to do just that; give both air and water. I only recently started paying attention to fertilizing, providing additional light besides a (large) window, and attempting to create a more humid environment (windowside terrarium).

But I'm afraid I overstepped a little for this ceramic growth experiment. Probably I should first try to improve my growing skills and then try my maniacal experiments on spieces that I am comfortable with.

I won't give up on this idea though. I'm continuing pottery classes anyway, so I might just aswell throw some and try some more variations. Yet I will take my orchids off the pots for now, and try to let them grow properly first.
The experiments with moss and perhaps some other plants will continue however.