Bonsai of climbing plants are among the most difficult to obtain, and are usually prepared only by bonsai experts. Climbing plants are very vigorous, and hence the difficulty of "reducing" them in the form of bonsai. The most common climbing bonsai are bougainvillea and wisteria. You start with a single well-developed stem that can sustain itself without the need of a trellis to cling to. Pruning for initial training is done while seeking to maintain the natural development of the climber, and then you have to try to encourage the development of a fake back, or the beginnings of a short arbour. In other cases, the vine is cultivated like any other plant, and then forms a short stem upon which rests an enlarged canopy, as if it were a tree. The development of climbing plants is very vigorous, and continuous throughout the growing season, so it is good to remember that pruning should contain this development, to prevent the plant rapidly returning to its original development, ruining the bonsai. After flowering you should shorten the branches frequently, keeping only 2-3 leaves on each branch; in this way the development of new shoots is encouraged, and the size of the plant will be contained.
Such vigorous development needs regular watering and fertilizing, so we prefer the use of slow-release fertilizer, to ensure a good standard of mineral salts constantly replenished in the soil. Watering will be administered only when the soil is dry, avoiding soaking the substrate. Vigorous plants often have an equally vigorous root system, so every two years, in autumn, you should uproot the plant, shorten the roots to about half their length and re-pot it using fresh potting soil, rich in organic matter.