Which substrate is suitable for your Calathea?
- boedefeld
- Jan 14
- 9 min read
You buy a new Marantaceae and might not think further about the substrate it was purchased in.
But is this substrate even suitable? And when would be the right time to repot?
Here you can jump directly to the individual topics:
What can be taken into consideration beforehand?
Right at the beginning, one should be aware that everything depends on the right substrate. Unfortunately, Marantaceae are very often sold in cheap, peat-containing soil, which does not provide a good foundation.
Peat-containing soil is generally unsuitable in the long term due to its properties.
Peat in the substrate will sooner or later become hydrophobic, meaning the soil will eventually no longer be able to absorb water and become compact. During this process, the soil can no longer be evenly moistened, which can lead to leaf damage or even root rot.
And: Leaf damage, such as brown or yellow spots, dried-up leaf edges, etc., is often due to an unsuitable substrate.
But which substrate is suitable for Calatheas? Let's take a closer look at that now.
What characteristics should a suitable substrate have?
Prayer plants can be kept very well in a variety of substrates or using different methods. There isn't 'THE ONE' right way, but there are indeed a few points that can be helpful when choosing the substrate.
Marantaceae prefer a substrate that distributes moisture evenly, retains it well, and is loose and airy.
These properties can be achieved 'classically' with a soil mix, but semi-hydroponics or even hydroponics are also very well suited for prayer plants.
What are the advantages and disadvantages of using a soil mix?
As mentioned above, care should be taken not to use soil containing peat. As an alternative, coconut-based soil works very well (e.g. 'KokoHum'), which can be customized and which can also quickly and evenly absord water again even after drying out significantly.
This already represents a significant advantage, because with a bit of experience and observation, you can easily and quite inexpensively create your own custom soil mix.
Coconut soil does not contain any nutrients for plants itself, so it is recommended to mix in worm humus or something similar.
A simple base to start with would be a mix of coconut soil, perlite and worm humus, which can be supplemented with additional coarse components, such as coconut chips or other nutrients. Alternatively, you can buy such a soil mix already pre-mixed.
Example of a coarse, suitable soil mix.
In addition to the positive aspects such as individual mixing ratios, even water absorption/distribution, and air permeability, mixing your own soil is relatively inexpensive and the individual components are locally available at any hardware store or garden center.
There is also the possibility that Marantaceae may not take the repotting of soil into other soil quite as badly as with some other methods. However, this is only a speculation based on personal observations and not a guarantee. Repotting always causes stress for the plants and can trigger individually strong reactions.
Like all substrates, using soil has not only advantages but also disadvantages. It is therefore up to each individual to weigh these and find the path that suits them best. Also through trying out, even if this may initially involve some possible losses.
Possible dangers when using soil are most likely that one ties their watering habits to a schedule, thereby turning the substrate into a home for pests, such as fungus gnats (provided they weren't already introduced with the soil).
Watering according to a schedule probably works only rarely, because plants, in different pot sizes or simply with differently developed root systems, all have individual water needs. And soil dries out at different rates here depending on various factors.
So you should always adjust your watering habits to the plant and ideally check the weight of each pot. Don't water all the plants on the same day.
And since soil is an organic substrate, it is naturally not shape-retaining, meaning it will have to be replaced sooner or later.
Tip: Using transparent pots makes it easy to monitor root development and the condition of the roots, allowing you to respond quickly to any complications (e.g. developing root root).
What is semi-hydroponics and what are its advantages and disadvantages?
Let's quickly clarify in advance what semi-hydroponics actually is. Although it has become increasingly popular in recent years, it may still be unfamiliar to some.
In semi-hydroponics, the plant is in an inorganic substrate, where water rises from the reservoir below through capillary action and can be absorbed by the roots.
Ideally, the pot insert should have a water level indicator, which makes it easy to monitor the water level in the outer pot. Individual, tailored watering for each plant is therefore no longer necessary here by checking the soil (dry/wet or pot heavy/light).
How semi-hydroponics works.
This creates the great advantage of semi-hydroponics or self-watering systems: you generally cannot overwater the plants as long as you keep the water level indicator at a medium level. A permanent 'maximum' reading on the indicator is not recommended.
It also reduces the colonization of pests that normally nest in organic substrates, such as fungus gnats or mealybugs, and unlike soil, it is shape-retaining, so it can be used over and over again after a single purchase.
If it is coarse enough, the mineral substrate also improves root aeration and thus reduces the risk of root rot.
Depending on how many plants you need to take care of, switching to a self-watering system can certainly save some time here and there. We will go into more detail about this elsewhere when we talk about watering, as there are a few points to consider.
For allergy sufferers, it might also be interesting to know at this point that allergic substances (e.g. fungal spores) are reduced with mineral substrate.
Because the typical smell of soil was gone, we were at least able to experience that our cats no longer get into the plants or the pots. Of course, this is just our subjective observation.
We ourselves have now switched all our Marantaceae to self-watering, and all our plants are in the 'Green Jungle Mix'.
(a German product)
Example of mineral substrate 'Green Jungle Mix'.
However, we do not want to overlook the disadvantages that this system entails at this point, as it is always important to get a comprehensive view before deciding on a substrate.
And a major point worth mentioning is the cost factor. For self-watering, you ideally need an inner pot with a water level indicator, an outer pot, and of course the mineral substrate. For (mostly) young plants, there are also self-watering systems equipped with a wick that draws water up to the substrate.
Example of self-watering with a wick system.
Of course, there is also the option of 'building' a sort of self-watering system yourself and forgoing a water level indicator. This reduces the purchase cost of special pot inserts, but you then have to diligently keep an eye on the water level in the outer pot or saucer. Finding an optimal and consistent water level here could also be more difficult, especially for beginners.
The substrate is initially definitely more expensive than soil in terms of initial acquisition costs, but these costs could balance out in the long run, as the mineral substrate only needs to be cleaned and can then be reused for the next plant - it is shape-retaining.
It could also, unlike soil, have issues with availability. Because even though you can buy mineral substrate pre-mixed or put it together yourself, not all garden centers or hardware stores carry the individual components or a ready-made mix. In this case, you would have to resort to buying online, which would additionally take delivery time.
Since we are talking about 'time', it should also be mentioned that repotting from soil into self-watering systems probably takes more time than repotting from soil into soil. Before a plant can be placed into the mineral substrate, it must first be completely freed from all its soil and the usually present root mesh, and thoroughly cleaned.
From our own experience, we would also like to point out at this stage that the cleaning process can potentially stress the plant further. You need to find a good method yourself that cleans the plant thoroughly (if you're not thorough here, you'll regret it later), but at the same time doesn't overly stress or even damage the root system.
Example of a Stromanthe in self-watering.
A final note: Substrates such as expanded clay or 'Seramis' are not suitable for the sole use in semi-hydroponics. These substrates behave differently in terms of water retention and release, and they can also lose their stability under constant moisture, which is present in self-watering systems.
What is hydroponics and what are its advantages and disadvantages?
Hydroponics can be explained briefly: here, plants stand in water without any additional substrate, and this method is also very suitable for Marantaceae.
The advantages of hydroponics are actually quite obvious, as it does not require any special containers/pots, no special substrate, and thus both the initial cost is relatively low and availability is ensured.
Similar to semi-hydroponic cultivation, pests such as fungus gnats and mealybugs are deprived of the substrate for nesting, and overwatering due to improper watering habits is also eliminated.
Sounds like the easiest method at first: just put the plant in water and that's it. But it's not quite that simple here either.
Because similar to semi-hydroponic culture, there are a few points regarding the water used that should be considered. More on this will be discussed in the section on watering and water elsewhere.
You should also make sure to clean the container regularly so that the water doesn't get musty and no algae form inside it.
In addition, once a plant reaches a certain size, it could become difficult to find a suitable container, and just like with semi-hydroponics, the plant must be thoroughly cleaned of all organic residues beforehand.
After we have now taken a closer look at some possible methods with their advantages and disadvantages, the question then arises:
When is the right time to repot my Calathea?
Here, one hears and reads a wide variety of recommendations. Sometimes it is said that the new plant should first settle into their new home, and other times it is said that you should repot them immediately.
And once again, the rule applies: everyone should decide the right timing for themselves. And if you're a beginner and haven't gained any experience in this regard yet, just try out to see what works best for you - or for the plants.
We would simply like to share a few thoughts and our own experiences on this matter.
First of all, we are talking about Marantaceae here; how it is with other plant families, we cannot and do not wish to comment on at this point. But prayer plants should ideally have similar conditions year-round, meaning plenty of light and temperatures not below 18°C.
Consequently, under these given conditions, it is basically possible to repot prayer plants year-round, since unlike other plants, they do not enter a natural winter dormancy. As they are tropical plants, one should ask: do they even know 'winter'?
Immediate or timely repotting of the plant as soon as it arrives at home has significant advantages.
First of all, the plant only goes through one phase of stress and not repeatedly at intervals. Moving into a new home already generally causes stress, repotting after x weeks causes stress again, and it is not guaranteed that the plant has already gotten used to the new home after those x weeks.
Honestly, it is not clear to us where the recommendation to wait a certain number of weeks comes from, because we have had plants that only settled in properly after half a year or even longer. And who would want to leave their Marantaceae in potentially unsuitable soil over such a long period of time?
This results in additional advantages, as unsuitable substrate can be directly replaced with suitable (or just fresh) substrate, which then provides the basis for strong and healthy growth, and at the same time, you can immediately check the roots and react if necessary.
Example of a weakened Goeppertia that was placed into moss to develop roots.
There are often concerns about repotting plants during flowering. In this regard, we have no negative experiences to report.
However, there are situations where you have to weigh whether repotting makes sense or if it's better to wait a bit.
Because here we are back to the topic of stress. Keeping that in mind, you should think twice about whether repotting is sensible for obviously weakened or sick plants. However, this is something to decide individually, and there are special cases here as well.
Conclusion:
Our conclusion on this topic is actually quite clear:
The best way to find the right substrate or method is by testing and experimenting yourself. The same applies to finding the 'right time' to repot the plants.
Of course, this can mean that you may experience losses, but that shouldn't discourage you!
You learn from it.
It only takes a few basic pieces of information to keep in mind along the way. And we've laid them out for you here.
Here you can find our blog overview for more interesting topics.
Comments