Quick disclaimer: I already made a more beginner friendly guide on !gruenerdaumen@feddit.org in German, which was more written for people who never came into contact with hydro. Here it is if you're interested meine deutschen Freunde :)
This guide only covers the technique itself, and is not about hydroponics in general.
Introduction
Have you ever wondered, if it's possible to create the perfect environment for every plant out there?
I did too, and now I can tell you, it's possible!
I have about 70+ houseplants alone sitting in semi-hydro (S/H), including orchids, ferns, cacti, calatheas, and whatnot. And they are all thriving!
Even with (comparably) very low maintainence!
Upkeeping this jungle would be impossible otherwise.
And these are only my indoor houseplants. It also works on other (outdoor) crops, like cannabis, chilis, herbs, and more!
How it works
To demonstrate you this setup, let me show you my small calathea. It has a nice clear pot, where you can see all parts the best, including the roots.
The backbone of this setup is the substrate.
For that, I use expanded clay balls, also called "LECA" or "hydroton".
It has the ability to be wicking, can store a bit of moisture, and, most importantly, it has many air gaps in between the pellets due to the form factor.
There's also the additional benefit that it's inert and it also will never decay, so you don't have to repot as often. Oh, and it's also very affordable :)
The pot is always standing ~1/3rd in nutrient solution. To ensure that, a water level indicator is added. That way, you will never have to guess again when to water!
If you plan to go on vacation, you can fill the pot up to the maximum line, and that will last you for weeks!
Don't use the full capacity too often tho, as it will create problems further down the road and should only be used as exception.
With a regular sized plant in a regular sized pot, I only have to water once a week, often only even once every two weeks when filled to the middle ("optimum") line.
Now, the magic begins. The plant will now begin to regulate itself and takes what it needs as it grows. How you may ask?
Because there is a gradient of different moisture zones in the pot.
The bottom third is 100% wet, and 0% air. When the plant is thirsty, it will form water roots that reach directly into the nutrient solution.
The middle half is balanced. Here, the LECA wicks up most of the moisture, and the balls are fully saturated and moist. The substrate can only store 30% of its weight in water, and the rest is air, even on the inside! The moisture is mainly upheld by capillary action.
And the upper few centimeters are (almost) completely dry. They will mostly act as a cover, so the moisture doesn't draw up too high.
(Btw, this is one of the reasons why we don't wanna fill up the reservoir too much, since that would shift the zones up too high and create a toxic fertilizer crust on the surface that can burn the plant when done in excess.)
You can see this phenomenon on said calathea.
The bottom roots look completely different than the upper ones.
Especially the upper roots have formed lots of root hair, which are often also called "air roots", while most of the other roots have established themselfes just right above where the nutrient solution surface is usually, and a few ones are submerged into the solution.
I never placed them myself that way, the plant did it itself! It just took what it needed.
Some moisture loving plants (like banana trees, calatheas, etc.) reach down almost completely into the reservoir, while others, like phalaenopsis orchids for example, can't stand having wet feet at all and establish themselves in the upper sections.
How amazing is that?!
Drawbacks (& care routine)
There aren't many, but still, there are a few ones.
First, transitioning plants from soil/ other setups to S/H is painful.
It will suffer a lot, and so will you.
If there's one single crumb of dirt left, it will rot. And some roots will rot anyway, no matter what you do. If you want tips, ask me.
Also, you'll need to "flush" the pot regularly. If you see the water level approaching "minimum", just swish the pot around a bit, that will loosen up debris. Then pour that in the drain, and top water it with your nutrient solution.
That will flush any accumulated salts and waste material down into the reservoir, and you can dispose it the next time.
I personally think doing that at least every second or third time when watering (basically, once a month) works the best. You don't need to overthink it.
Anyway, this post is already longer than expected. If you have any questions, ask. I know everything about that topic :D
Bonus (& tips)
Here are some random pictures with information for you! :)
These are commercial hydro pots. I can highly recommend buying those, instead of going the DIY-route.
If you still wanna build one yourself, because those inner hydro pots often don't fit into normal outer plant pots, I strongly recommend you to use orchid pots instead of nursery pots. They have way better airflow and you can see the roots better.
Also, zip-tie the indicator to the pot for easier lifting :)
Here are the roots of two different plants. See how different they look!
I've noticed that some (peat loving) carnivorous plants don't like hydro, while others still thrive in it
Here's me growing potatoes and weed
And here are a few of my calatheas (or similar)
Some of them have a few crispy tips, either due to the initial transition from soil to hydro, or because I completely forgot to water them. Never ever let your reservoir run dry! This can severely damage the delicate root structure!
Most of them are less than half a year old, and they even grew so much in winter that I was able to divide the root stock and propagate them!
Now, summer is starting, and they just explode with growth! It feels like they almost push out leafes daily and look incredible vibrant!
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