The fertilizations are fundamental for having luxuriant and healthy plants, above all if these are cultivated in pot. The plants draw their nourishment from the sun and from the air, through the chlorophyll photosynthesis, as it happens for the other living beings but, besides the sugars, they also need mineral salts and water, which they take from the ground, through the roots.
We could call the fertilizers "mineral salt supplements", like the ones we happen to take for ourselves in the pharmacy; in the formulation of fertilizers for plants we generally find two groups of minerals, on the one hand the macroelements, Nitrogen, Phosphorus and Potassium, which are indicated by the symbols N, P and K: they are the minerals that plants use most. On the other hand we find the microelements, which are varied, from magnesium to iron, from calcium to boron. As far as macro-elements are concerned, they are always present in any fertilizer, but their concentration varies; microelements instead may not be present in a fertilizer, or we could find some but not others, depending on the plant for which the fertilizer is formulated.
The nitrogen is fundamental for the plant during its entire development, but above all in the periods in which the plants sprout and produce new branches and foliage; therefore spring fertilizers are generally richer in nitrogen; Phosphorus, on the other hand, is fundamental during the flowering period and during the period in which the fruits develop; Potassium guarantees colorful flowers and tasty fruits. In general we can say that nitrogen is the element that is consumed in greater quantities by the plant, while phosphorus and potassium are needed in smaller quantities.
All the other microelements are fundamental in the various phases of plant development; some are more important for some plants than for others: for example, iron is used above all in greening fertilizers, to be supplied to acidophilic plants that stay in poorly acid soils; or for example aluminum is given to hydrangeas to color blue flowers more.
When buying a fertilizer it is good to check the descriptive label to know the quantities of each element present in the fertilizer itself.
Fertilize in the apartment
In nature, plants draw the mineral salts they need from the soil; in a forest a large tree has a huge volume of soil at its disposal, in which it sinks its roots; over time, this soil is constantly enriched, thanks to the decomposition of the leaves, the droppings of the forest animals, and the rocks through which rainwater passes. For this reason the tree of the forest is always healthy and luxuriant and develops without problems, enjoying the succession of the seasons and the external climate.
In the apartment our plants are grown in small pots; the land they have is only that, and we often forget to repot them even for a few years.
For this reason it is essential to know how to supply and dose fertilizers, otherwise our plants will certainly suffer from deficiency diseases or excess fertilizer.
Fertilizers in the apartment: How to choose fertilizers
It is very important to choose which fertilizer to supply our plants; not all plants use the same quantity of the various elements that make up a fertilizer, and the same plant needs more or less quantities of a given mineral salt during any time of the year.
For example, as mentioned above, nitrogen is useful in the development of new branches, shoots and foliage: therefore, during the period from the end of winter to spring we will supply our plants with fertilizers richer in nitrogen.
During the spring period instead we will prefer a fertilizer rich in potassium, for plants that have a rich flowering.
We choose a specific fertilizer for each plant we have at home: it is not appropriate to buy a "universal" fertilizer, but it is preferable to choose a fertilizer for green plants, one for flowering plants, one for orchids, one for succulents; in fact, these compounds are better suited to every type of plant, thus avoiding adding minerals to the soil that are not used by our plants.
We also check on the various packages the amount of mineral salts dissolved in the fertilizer we are buying: some fertilizers cost much more than others, this is often due to the higher concentrations of elements present in them, so the cost for each individual fertilizer is less .
How to provide it
To better regulate the amount of fertilizer inside the pot it is advisable to supply it several times but in reduced doses: if on the package we read to use for example a cap every liter of water every 15 days, we prefer to add half a cap every liter of water every week. In this way we will make the mineral salts available for a longer period of time, avoiding periods when the salt is present in greater quantities.
Let us remember that all the plants tend to go through a period of vegetative rest; during this period it is not necessary to supply fertilizers, which would remain unused in the soil, saturating it excessively. Generally this period is the winter one, except for some exceptions: for example the poinsettias tend to bloom in the late autumn period, therefore we avoid to fertilize them in the summer but we supply them with fertilizer in the autumn; for other exceptions let's turn to our trusted nurseryman who will know how to indicate the period in which to avoid providing fertilizer to our plants.
In addition to liquid or powdered fertilizers, to be added to the water used for watering, there are slow release granular fertilizers; these fertilizers are spread on the ground, and will tend to melt with watering; if we always water the plants supplying the water in the saucer put the granular fertilizer in the saucer. These fertilizers are supplied in late winter and sometimes in summer, a dose of fertilizer dissolves over 3-4 months.
Some plants do not particularly like contact with mineral salts contained in fertilizers; for example, most carnivorous plants do not tolerate even the smallest amounts of nitrogen in the soil; these plants in fact extract the nitrogen they need from the digesting insects: therefore we avoid supplying nitrogen in any form to carnivorous plants, which otherwise tend to dry up quickly, as if burned.
The part of cacti and succulents does not like excessively rich nitrogen fertilizers, which tend to produce turgid and water-rich tissues, which can easily be affected by rotting; for succulents we prefer fertilizers with a very low nitrogen content, rich instead of potassium, which also favors flowering.
The roots of orchids do not tolerate the presence of mineral salts in direct contact, especially for prolonged periods of time; when we supply a fertilizer to the orchids let's do it by preparing a large quantity of fertilizing solution, in which we will immerse the whole vase, for about 15-20 minutes. At the end of this period we raise the jar and let it drain before placing it in the saucer.