There are 2 species of wisterias, wisteria sinensis and wisteria floribunda. The second smells more intensive and the flowering season is longer, from may to june and august to september. The leafs are of a light green color and in the flowering season they form dense bunches of violet flowers.
Temperature and exposure: Wisterias love the heat and it is supposed that they don't like freezing temperatures. I have a wisteria bonsai and wisteria plants outside and they withstand freezing temperatures quite well. Protect against temperatures below -5° C.
Pruning and cleaning: Pruning of the new and thin branches: Always after the flowering and before the leafs harden, prune the new branches with the scissors. Prune with care to not damage the tree as this will affect the next years flowering. In autumn, when the leafs have dropped, you can do the structural pruning. Pruning the older branches: After the flowering, prune all the unnecessary branches with care.
Light: Let them have as much light as possible as this will be favourable for an intensive flowering.
Repotting / Soil: Repot every year right after the first flowering period, that is may to june, as the growth of the wisterias is very vigorous. I like wisterias in big dark brown pots as the pot shown in the photograph above.Wisterias like fresh and light soils, the mixture I recommend is composed of 1/3 of organic material, 1/3 of humus, 1/6 of sand and finally 1/6 of akadama.
Wiring: Wire from spring to autumn with care when the branches are still easy to bend, once they get hard use raffia to protect them from breakage.
Watering: Water frequently, especially in summer as the plant needs a lot of water, but be sure that the drainage of the pot is effective too. After the repotting you can water the bonsai 2 or 3 times a day. One moth later reduce to dose to one time per day or even one time every two days. In summer, place the pot in a bowl of water and let it absorb as much water as possible. Repeat this process about three times to four time waiting 5 days between the processes. This will favour the flowering and this way they will flower every year. Only vaporize when the wisteria has no flowers.
Fertilizer: When the flowering has stopped, administer a liquid organic fertilizer. Also apply solid fertilizer. In autumn add again liquid fertilizer and the add again of the solid type. Wisterias need much more fertilizer than other bonsais because of the very intensive growth and flowering.
Diseases: I cannot give any advice on remedies on diseases or plagues by now, as it is the first year of this plant as bonsai, on the rest of wisteria plants I have suffered no diseases or plagues by now.