Question: Pruning and repotting
A few days ago I bought a zelkova ulmus parvifolia bonsai and once at home I realized that the bonsai has a structure similar to the informal upright style but has an excessive sloping in all the branches that I cannot correct with the wire because they are now thick and woody. So, after the bonsai has settled in, I would like to do a pruning but it's not good how to behave, I would also like to replace the unsuitable soil that it now has: do I have to behave?
the zelkova is widely used to form bonsai, both because it is one of the saplings traditionally used in Japan, and because it is able to adapt quite well even when the cultivation conditions are not perfect, and therefore it allows to learn to cultivate it through small errors. As for the repotting, unfortunately very often it happens to bring home from the bonsai nursery that seems to be in the same land for several years, and the period of time depends on when the inexperienced bonsai nurseryman has bought the bonsai from a producer; for this reason it often happens that bonsai suffer (or even die) already in the first weeks of nursery-home transfer. My advice is usually to repot as soon as possible; now however we are already in spring and therefore the repotting could be excessively stressful for your plant; then consider if you think the soil is in such a disastrous state that urgent intervention is needed; or if instead the soil would have to be changed, but the plant could survive in this substratum at least until the autumn. Because the zelkoves should be repotted after they have lost their foliage, in autumn or in late winter, so that they are already in the new land when spring arrives. If indeed the earthen bread is stiff and compact, and shows some exhausted earth, you can even think of potting out your zelkova, but postponing the cutting of the roots in the autumn or next year at the end of winter. In the repotting it uses a very well draining soil, consisting of universal soil of excellent quality, mixed with pumice stone and akadama. As for pruning, the zelkova tends to respond very well to the toppings of the branches, so much so that it is often pruned more or less once a month; if, on the other hand, you have to take away entire branches, even here it would be appropriate for you to be patient, to intervene only when the tree has lost its foliage, in autumn or in late winter. Now that the plant is already in full vegetation it is not the case to go to practice very heavy prunings, because you would cause a strong loss of sap from the cuts, and the operation would be a very strong stress for the whole tree; if you also decide to repot it, such a shock treatment, practiced in early spring, could be decidedly excessive. If it were my bonsai, and it was in a very bad soil, I would immediately return with top-quality soil, perhaps taking the bonsai in shade for a few days and not in an excessively sunny place; and then I would begin to trim the branches more protruding from the crown, making some small pruning; for pruning more training instead I would wait until next autumn.