Repotting is an important and extremely delicate operation for bonsai care and must be repeated often during the life span of a bonsai, a bad intervention can affect the future and even the life of the plant itself.
It consists of the change of the earth inside the vase that contains the bonsai and in the possible replacement of the larger vase to give more space to the plant if the right proportion between the vase and the plant is lost or if the bonsai is already of the desired size. , leave original or replace it with one of equal size.
Repotting also results in a reduction in the extension of the root system, thus favoring the emissions of many root hairs which, thickening in a small space, are the main architects of the plant's absorption and nourishment.
The frequency with which a Bonsai must be repotted depends on the size of the pot and the species of the tree, therefore, fast-growing trees need to be repotted every two years (sometimes even every year), while the older ones need to be repotted. mature must be repotted within a period of 3 to 5 years.
Deciding whether to repot a bonsai or wait depends on several factors to be taken into consideration: the actual needs of the plant, the aesthetic factor that it is intended to maintain or achieve.
In any case the repotting procedure should always be done when the plant is in good health so as to allow the plant to overcome the stress deriving from repotting in the best way.
The main reasons for repotting
The reasons for repotting are different:
soil depletion: with time the nutrients of the earth are running out;
root growth: with the growth of the roots the bonsai tends to rise from the ground or rather make the ground bread rise up while the grown capillaries can create a blockage in the drainage of the pot or escape from the holes in the pot;
bad drainage: that is to say, water cannot be seen coming out of the holes in the vessel;
the soil is too compact: it is the case of the clayey soil like that of exported bonsai, this type of soil, excellent for retaining humidity, has the defect but once dried it becomes almost water repellent, ie the water has difficulty penetrating it .
When to repot
Bonsai repotting does not follow the general rules that apply to common ornamental plants.
The best time for repotting is the rest period that precedes the vegetative season, generally the best periods are spring and autumn depending on whether they are outdoor plants (maples, oaks, elms etc.) that vegetate in spring, repotting. should be done in winter, if the species of bonsay are outdoor plants (Maples, Oaks, Elms etc.) that vegetate in spring, instead, being tropical genera that vegetate in the summer repot in the spring.
In this way, by observing this period of rest, the traumatic effect of repotting on a tree is minimized precisely because the tree does not yet have to maintain a mature vegetation.
Generally a bonsai should be repotted every two years, but this frequency is purely indicative and is influenced by various factors, such as the age and the species of bonsai, it is necessary to distinguish between young plants that grow faster and need to be repotted every year as for example the Ficus, the Olmi, the Carpini etc., from the older plants that vegetate more slowly should be repotted every three or four years, examples are the Pines, the Junipers and evergreens in general.
Repot bonsai: Choice of pot and preparation
To start the repotting operation it is necessary to prepare the pot, but before that, to choose it, the choice of the most suitable pot both in size and in style is of fundamental importance for the composition as a whole.
It is certainly a choice conditioned by multiple factors, both botanical and aesthetic, depending on whether you want to grow bonsai, you need to replace a vase with a larger one but always rather low to avoid the growth of roots down, in the case instead the bonsai is already of the desired size and maintaining the right proportion vase-plant, or using the original vase or replacing it with one of the same size.
Once the pot is chosen, it is necessary to sterilize germs and pests, drill holes for drainage if there are none and fix a net with a copper wire to them, the meshes of the net must be thin to allow the exuberant water of drain, prepare the bottom with akadama draining material, pumice pumice, etc. and add a layer of soil before going to place the bonsai
At the time of repotting it is advisable to choose a place in the shade and sheltered from the wind and always keep a nebulizer for the roots within reach if needed.
Having to transport the bonsai from one container to another it is advisable to work with dry soil, this is because it makes it easier to separate the plant from the old container and to arrange the roots more easily in the soil.
To remove the bonsai from the old container you must never take it by the trunk because it would lose many root hairs, it is advisable to remove it by turning the pot upside down and gently tapping the bottom to let the plant out, in case you were struggling to get out you can provide with a not sharpened stick by pressing on the drainage holes.
Once the bonsai is freed from the container, the roots are freed from the old earth, always with the help of a stick gently trying to free the roots from the soil, this is an operation that takes time and patience, if the roots are rebellious or too long they must be reduced by a third of their length, the broken or dead roots must also be eliminated, popped, in case it is present, the taproot is the main root of the whole root system.
Once the pruning is finished, place the bonsai in the pot where a layer of soil has already been laid, always proceed with the help of a stick to spread the roots in the first layer of soil and, once the right position of the bonsai, more land is added without however filling the container to the brim, gently pressing it with the stick to avoid pockets of air harmful to the root system.
Once the repotting is completed, the plant is watered abundantly or, if preferred, it is immersed in the water of the pot itself up to the edge and settled for twenty days in a shaded environment sheltered from the wind.
The fertilizer is administered only after a couple of months from the repotting.