If you have not yet visited the indoor plants section , we recommend you take a look. We talk about the care of them and among those cares, is the choice of a good substrate. We tell you the most common and we will see their characteristics. We’ll leave one undescribed to see if you can figure it out. Comment on the entry to see who is able to tell us which one is missing! Lucky!
Index
PROPERTIES OF A SUBSTRATE
The substrate that we use has to meet basic and not so basic conditions for each plant. Normally, the plants we use are adapted (and not so adapted) species brought from other countries, even continents.
This means that we must simulate as best as possible the conditions of the environment where they were originally developed, if we want optimal results and an unprecedented plant variety . For that we must start, as if it were a house, with the foundations.
The first thing to keep in mind is that the substrate for physicochemical purposes does not have the same characteristics as a soil. A substrate will be much more aerated in relation to the low weight generated by the volume contained in the pot or planter, for example.
But perhaps the most important difference is the organic matter content .
To this day, a soil with 3% organic matter is considered a good soil. The vast majority are between 1% and 2% (in Spain at least) and sometimes we do not even reach 1%.
However, a substrate can perfectly reach levels of 70% in organic matter, even being close to 90% in some cases. Other important factors for the choice or creation of substrate will be the porosity or air exchange capacity , and the water retention capacity .
In the latter, it is also important not only the ability to retain it but also the amount of it that is available to the plant.
The last characteristic of a substrate although it may seem obvious, is the support for the development of the plant. Let’s see the different types:
NATURAL SUBSTRATES
SUBSTRATES FORMED BY SAND
This is one of the substrates that is used the most due to its ease of use, granulometry and because it gives us a good general drainage by homogenizing well with the rest of the substrate components. The best sands for this purpose are river sands.
They have a medium water retention capacity . The only problem that we may have, unlike gravel for example, is that over time we will lose a little of the aerial phase due to compaction, therefore the aeration capacity will decrease slightly.
Another interesting aspect is that they hardly degrade over time.
SUBSTRATES FORMED BY GRAVEL
Another widely used substrate as well. Good structural stability, low water retention capacity (draining), but its porosity is high, thus favoring the general aeration of the substrate. They are also very stable like river sands, so we will have gravel for a while.
The best are those made of quartz, and those with little calcium carbonate content. Pumice stone is another interesting one, but it must be washed before use.
SUBSTRATES FORMED BY VOLCANIC GRAVEL
It goes without saying the provenance of this material. Composed mainly of silicon and aluminum oxides among others.
As advantages we could say that it contains some micro and macronutrients such as calcium, magnesium and phosphorus. The pH is somewhat acidic and its water retention capacity is practically nil.
SUBSTRATES FORMED BY PEAT
Blond peat
Just as the three previous materials could be considered inert, in peat we have already gotten a little out of that clisification. Peat is the first phase of formation of mineral coal from plant remains.
Its composition is highly variable . We distinguish between blond (sphagnum) and black mobs. The former less mineralized and therefore with a higher content of organic matter are widely used in seedbeds, for example.
The real good blond mobs are those made up of remnants of mosses from northern Europe . Black, quite the opposite. They have more mineral content, but they are also more stable.
When buying peat we have to be more careful than with other substrates. When varying its composition depending on its origin, we must take it into account.
COCONUT FIBER COMPOSITE SUBSTRATES
Coconut fiber: We have already talked a little about it in the post dedicated to the sowing substrate for garden vegetables .
It is widely used for this purpose.
It has a very good water retention capacity and at the same time good aeration capacity. It usually contains salts so it must be washed. Anyway, ask where you buy it because it can come ready to use.
MANURE-RICH SUBSTRATES
Manure : Obviously, we are not going to put manure directly into our pot for a houseplant. We would have a slightly strong air freshener ;-). It must be previously treated, composted and decomposed for direct use in a pot. It has a high content of organic matter. It will also depend on the type of manure in question and its level of composting. Its water holding capacity is very good too.
EARTHWORM HUMUS
The king of all hummus !!
Much has been said about this type of compost wisely made by the Californian red worm. We owe a lot to this little annelid. This substrate is one of the best today. Its contribution in available nutrients is exceptional, in addition to improving the structure of the substrate and its chemical composition. If you want to know more we recommend you see the entries regarding compost and vermicompost.
PINE BARK
It is also widely used. Of the barks it may take the palm. It is used both fresh and composted. The last case is the most recommended. Those that are fresh can cause phytotoxicity problems. It has good aeration capacity and its water retention capacity is medium-low.
ARTIFICIAL SUBSTRATES
In some cases we may need some of these substrates because they may have properties necessary for a specific case. Some of the artificial ones such as expanded clays or pearlites and vermiculites have excellent properties.
Let us begin:
PERLITE SUBSTRATES
This is one of those examples we were talking about.
Great water retention capacity , up to 5 times its weight, but in turn, great porosity. It is an excellent component that comes from volcanic gravel to which a heat treatment is applied to acquire these properties.
Widely used together with vermiculite in substrates for seedlings. It also has an acceptable durability, around 6 years.
VERMICULITE
Mineral belonging to the micas family composed of aluminum, magnesium and iron silicates which is thermally treated, acquiring a much higher volume than the original. This expansion is what gives it the characteristics of high water retention capacity and aeration capacity, although the latter is lost over time due to compaction, as is the case with sands.
ARLITAS
Also known as expanded clays, they must also be heat treated so that they acquire a volume much greater than their weight and gain in porosity. That is its great virtue, since on the other hand we have a low water retention capacity.
ROCK WOOL SUBSTRATE
Made from volcanic rock, it is widely used in the construction industry for its fire-retardant and sound-absorbing properties, but it also has its application in creating a substrate for plants.
The advantage of this material is that it has a good water retention capacity and at the same time achieves acceptable aeration. It can degrade over time.
You have an entire article dedicated to rock wool.
Rock wool cell tray
EXPANDED POLYSTYRENE
Although it is a plastic, and in Gardenprue we do not like it too much, it has been and continues to be used as an aerating component for many substrates. Its low price may be a good reason for its common use.
It has a low water retention capacity.
COMMERCIAL SUBSTRATES
This is the easy way, but no worse for it.
Obviously we will have a selection of general substrates, such as the universal substrate, which will serve us for the vast majority of plants but not optimally.
There are also specific substrates for cacti, for acidophilic plants, and a myriad of them that are formulated for specific species and plants.
If you have doubts, it is best to ask wherever you go to buy.
There is no better or perfect material to make a substrate. This is like cooking. The right mix of ingredients is what makes a great dish. The same thing happens here.
The right mix of materials is what gives the physicochemical characteristics necessary for each plant.