Posted: 08/04/2016 at 19:32
I'm certainly not "the expert" mentioned in a previous post, but I have made suggestions in the past ref caring for wisteria. As others have already said, it can take many years before a newly purchased plant may flower, so it's a good idea to buy one when it is actually flowering so that you know there's every chance that will continue to do so thereafter.
When I came to my current home - over 20 yeas ago now - there were two very well-established wisterias at the property but neither of them flowered. I found this very frustrating, as the plants themselves had clearly been there for many years with the main stems being at least 3" in diameter. They had been planted at the front of the house, at the base of the house wall, in rather small holes which had been made in the concrete path which ran along the whole of the front. I discovered that they needed to be very well-watered during the autumn months, in order for them to flower the following spring. I made sure that they got lots of water until the time came when the path itself was removed in order to create a shrub bed in its place, together with a new layout for the driveway etc. Since then the general rainfall has meant that the moisture spreads throughout the shrub beds and extra water for the wisterias has proved to be un-necessary.
The reward has been what could be described as resembling a purple waterfall down the whole of the front of the house - and it's turned out to be one of those things which people use to identify the house itself - i.e. "that one with the fantastic wisteria".
My guess is that not only lack of water but also lack of nutrients played a part in the poor "performance" of the plants - the soil close to the house foundations was probably very poor quality and the concrete path certainly meant that there was insufficient water reaching the roots.
It doesn't work, however, to use too much fertiliser because this stimulates leaf growth rather than flowers, so careful and regular watering seems to be the solution.