Dear site, I have been following you for some time, for I was unable to find an explanation for my problem. One information, I have a bonsai, to be precise a ficus retusa (bought in early February) I can’t understand why it has become so impossible to keep, I explain: near a window, it has no excess water, it does not take cold currents (at least I hope, unless there is some draft in the window) if above the dry earth I water it by immersion (for about 5 minutes, then I remove it from the saucer and go back to where before), it continues to lose the leaves and then dry the sprig from the tip. Where am I doing wrong? if you prefer I can send you some photos. Looking forward to your reply, thank you, greetings.

Dear Riccardo,

the genus ficus gathers a large number of species of trees of variable size, and also shrubs of various types; the ficus we are most used to is a Mediterranean species, the ficus carica, that is the fig we are used to eating the sweet and soft fruits. The ficus grown in apartments are more often species of Asian origin, and so also for the ficus retusa, a typical ficus bred as bonsai, native to Malaysia, and therefore used to a mild climate, mostly warm, and quite humid. Grown as bonsai, in the apartment, it is a small tree that is easy to grow, very widespread also due to the fact that it tolerates drought well, and therefore also suitable for the most careless growers, who periodically forget to water their bonsai; the ficus retusa in fact does not require excessively abundant watering, and even if from April to September it is important to water it every time the soil is dry, in the remaining months it is sufficient to water it sporadically, about once every 15 days, or even less. This is because, even if it is an evergreen plant, in the months with short days, the ficus retusa tends to have a semi-dormant period, in which it does not need much water; so in spring and summer, your perfect immersion watering method: immerse the pot with water that reaches the outer edge, as soon as the soil on the surface gets well wet, take the pot out of the water, let it drain well and put it back in its place . In the autumn and winter months, on the other hand, you can simply water the soil lightly, with a little water, once in a while. In the growing season, in addition to water, also provide fertilizer, specific for bonsai, every 15 days. In my opinion, from your description of your ficus, it received too much water in winter, and is now developing root rot; therefore the case of repotting it, replacing all the soil with fresh soil and also pruning the roots in the points that you notice dark or damaged, obviously without exaggerating. In the descriptions of this bonsai, it is often indicated that it is a plant that, while tolerating a periodically dry climate, actually loves humid environments. This does not necessarily mean that it should always be watered all year round, simply, in the winter period, it is advisable to vaporize the leaves with demineralized water, in order to increase ambient humidity; this is because in the house, the heating system, any stoves or fireplaces, and the proximity to a radiator, tend to dry the air very much, making it unhealthy for all plants; this problem is solved with a simple vaporizer, with which to spray the water on the leaves of the plants. Surely it is also useful to place more plants close together, so that the vaporization is carried out for a longer time, and the climate in their vicinity tends to become slightly more humid.