Ruined bonsai leaves

Question: what happens to my bonsai?

hi I have a bonsai kept at an angle near the window far from the radiator. Every year it loses its leaves, then it is reborn, but for a year the leaves have a brown terminal part. I state that there are new leaflets but some branches look dry. Thanks

Ruined bonsai leaves: Answer: grow bonsai

Dear Lucrezia,
bonsai are delicate plants and need special attention, but despite this over the years they become real fighters, able to survive even if subjected to truly anomalous and poorly adapted living conditions; the plants normally lose their foliage for two reasons: because they are deciduous plants, and therefore when the days shorten they enter vegetative rest; or because they are kept in completely wrong conditions, so they suffer, or are attacked by pests or diseases.
There are also varieties of plants with an intermediate behavior, that is when the climatic conditions become excessively critical, they enter in vegetative rest, losing the foliage.
In your case it is not easy to understand what situation we are in, not knowing what plant it is.
Since your bonsai has lost its leaves every year, but despite this it has survived, it is thought that it is a semi evergreen plant, which under stress has lost its foliage and then has quietly sprouted, but it is not said. It sometimes happens that deciduous plants are grown at home, that they would prefer to spend the winter in the garden, or on the terrace; perhaps in a sheltered area, or covered with non-woven fabric, but still outside.
In any case, it is important that you do research to establish what plant it is, because it is clearly showing that it is not in an area where the climate, humidity, brightness, are welcome; so do some research on the internet, trying to figure out if you have an outdoor deciduous plant, an apartment bonsai, a delicate bonsai. In fact it is not so difficult, as the plants that can be bought already bonsaized in nurseries generally do not belong to several tens of different species or varieties; in Italy the most common bonsai are ficus and carmone, maybe you have one of these two.
However, usually the main problems related to the cultivation of bonsai, which cause browning of the leaves, and sometimes even the total or partial loss of the foliage, are generally attributable to two problems: watering and fertilization.
Not knowing what plant it is, it is not easy to give valid advice; but I remind you that plants are living beings, as such they have different needs depending on the season. Even when they stay at home throughout the year, they can behave in the normal course of the seasons, as their lives are linked to the number of hours of daylight.
So remember that it is not desirable to cultivate a plant throughout the year in exactly the same way: fertilizers are supplied during the period of greatest vegetative vigor, from March to September; also because the mineral salts they contain are not food for the plants, but we could consider them as the vitamins that the doctor advises us to take in spring (the plants do not feed through the roots, but through the leaves, with photosynthesis). Watering must be different depending on the season and the positioning of the pot: it is watered when the soil tends to dry out, avoiding stagnation, and also avoiding leaving the pot completely soaked or completely dry. If your plant particularly likes humidity, it should also be vaporized during the winter (when the heating system is active), and during hot and humid days in the summer.