A few days ago I bought a bonsai of zelkova ulmus parvifolia and once at home I realized that the bonsai has a structure similar to the informal upright style but has an excessive slope in all the branches that I cannot correct with the wire because they are now thick and woody. After the bonsai has settled, I would therefore like to prune but it is not good how to behave, furthermore I would like to replace the unsuitable soil it has now: what should I do?

Dear Giulia,

zelkova is widely used to form bonsai, both because it is one of the small trees traditionally used in Japan, and because it is able to adapt quite well even when the cultivation conditions are not perfect, and therefore allows you to learn how to grow it through small mistakes. As for repotting, unfortunately it happens very often to bring home from the nursery some bonsai that appear to have been in the same land for several years, and the period of time depends on when the inexperienced bonsai nurseryman bought the bonsai from a producer; for this reason it happens very often that bonsai suffer (or even die) already in the first weeks of the nursery-home transfer. My advice usually is to repot as soon as possible; by now we are already in spring and therefore repotting could be excessively stressful for your plant; then you evaluate if in your opinion the soil is in such a disastrous state as to require a very urgent intervention; or if, on the other hand, the soil would need to be changed, but the plant could survive in this substrate at least until autumn. Because zelkove should be repotted after they have lost their foliage, in the fall or late winter, so that they are already in the new land when spring arrives. If indeed the bread of earth is rigid and compact, and it shows some dead soil, you can think about potting your zelkova even now, postponing for cutting the roots to autumn or next year at the end of winter. When repotting it uses a very well draining soil, consisting of universal soil of excellent quality, mixed with pumice stone and akadama. As far as pruning is concerned, the zelkova tends to respond very well to the topping of the branches, so much so that it is often pruned more or less once a month; if, on the other hand, you really have to remove entire branches, even here it would be advisable for you to be patient, to intervene only when the tree has lost its foliage, in autumn or at the end of winter. Now that the plant is already in full vegetation it is not really the case to go and practice very heavy pruning, because it 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 decide to repot it too, such a hard treatment, practiced at the beginning of spring, could be decidedly excessive. If it were my bonsai, and it were in a bad soil, I would repot immediately with top quality soil, perhaps keeping the bonsai in partial shade for a few more days and not in an excessively sunny place; and then I would begin to trim the branches protruding from the foliage, carrying out some small pruning; for more training pruning instead I would wait until next autumn.