The potting soil plants on the balcony, on the terrace and in the house must be a little different from what the same original plants find in nature. This is simply because the climatic and environmental conditions of the confined spaces are different from those of the garden, starting with humidity and brightness.
This is why we find many on the market soils per vase ready to use for cultivation in pots, some of natural origin and others derived from synthetic products. There are 'universal' ones and specific ones for particular types of plants, for example acidophilic plants, more or less rich in fertilizer. But what if we wanted to do it alone?
Well yes, a good one topsoil for the vases however, you can also prepare it yourself, by mixing the 'basic ingredients' according to the plant it will have to support. This is probably the cheapest way to have soils perfectly suited to the individual essences without having to buy a hundred different bags that will mostly remain unused. Here are the basic ingredients that we can keep available on the balcony.
Garden soil. The garden earth, easy to obtain, is certainly the starting point for the preparation of potting soil and can in itself constitute the natural substrate of many species. However, it must be examined carefully: a good garden soil to use in pots must not contain stones or pieces of roots (clean it before use) and should consist of: about 50% of sand, about 25-30% of silt ( see peat), 15-20% clay, 10-15% decomposed organic matter. If these elements are not balanced in the soil you have available or if the plant that will go into the pot has other preferences, you can make the necessary corrections yourself.
Peat. If the topsoil it is too hard, add peat to make it softer, especially more for sowing and planting cuttings. Also keep in mind that several plants require the presence of peat in the topsoil in larger quantities than can already be found in garden soil, so you may need to add it. Peat also includes silt, which is in fact a sedimentary peat, and is classified on the market based on the color and the degree of grinding that determines its structure. The most suitable peat for potted plants are the coarse-grained blonde ones that allow good air passage and a fair amount of water retention. Dark peat, less suitable for pots, can be mixed with sand and perlite.
Baked clay. Unlike peat, baked clay is used to give consistency to soils too light. Baked clay should be confused with expanded clay and increases the compactness of the topsoil together with the ability to retain water.
Soil of leaves. It is a composition that you can prepare yourself in a box on the balcony or terrace by mixing the earth and leaves of some trees, in particular beech and pine. It can be used on its own or mixed with peat for plants that want a soft, nutrient-rich soil, or to amend garden soil that is too lean. The pine needle soil is suitable for acidophilic plants, but better to avoid the needles of Picea and Abies because they contain too much resin. But be careful: collecting leaves in the woods is prohibited by law.
Bark. It is found on the market (often with the name of bark) and it is good that it is treated to eliminate resinous substances. It is used to improve the absorption of water and the passage of air, has good ability to retain moisture and is usually used to correct peat.
Sand. It is used to correct peat or other organic materials in order to make the soil more draining, but it can also be used alone for the planting of cuttings with the addition of fertilizer. The most suitable sand is the fine river sand, light gray in color without gravel.
Perlite and vermiculite. They are inorganic materials that are obtained from some rocks. They are used to give the soil greater softness, permeability and aeration especially for sowing and rooting.
Compost. It is the fertilizer obtained from the natural decomposition of organic substances through the combined action of oxygen and bacteria. It is used to fatten the topsoil and immediately make available to the plants the nutritional elements they need, and which can then only be integrated with fertilization. Compost can be purchased in bags (read the composition on the label carefully) but you can also do it yourself with home composting on the terrace.
An important thing to know before planting plants is the ph of topsoil that you have prepared, on which the chemical fertility of the soil depends. Most essences like a pH around neutrality (which on the scale from 0 to 14 means around 7), but there are, for example, the acidophiles that ask for some acidity (heather, rhododendron, azaleas ...).
Also for the measurement of the ph of topsoil you can do it yourself by getting litmus papers, distilled water and small containers available in pharmacies or specialized stores. Or, simpler, get yourself a soil pH analog meter