My wisteria

Hi. It can be quite confusing I admit. Basically, there are two prunings but only after your young plant has covered the framework that it is climbing on. Once it has done this and all stems tied in, these then become the permanent stems that you prune back to.

Shoots produced from then are indeed pruned around August half back. Then once more in mid winter (get you woolies on) further back again to about three buds. These become the flowers for next year.

By first halving the length of the new shoots, this initiates the beginning of flower buds at their bases. The remainder is removed back to three buds in winter as it is only these basal buds that flower, the rest of the stem will just be growth buds.

If you are wondering why you can't just prune back to three buds in August, it's because if you did, these three basal buds would just start to grow into new shoots and no flowers. By leaving part of the shoot on, this fools the plant (if you like) until they are removed in winter when it is too late for the plant to do anything about it.

The secret to getting your wisteria to flower is basically starvation, all the above advice is excellent and the best description I have seen so far of the pruning regimen, well said Fractal

The wisteria is a rainforest plant originally and is subjected to conditions which make it grow and flower, basically the rainforest soil is very deficient in many of the things which usually make plants grow and flower as the nutrients are washed out by all the rain. The soil is also very free draining, so to imitate its original conditions is the way to promote flowering. Plant where it is very free draining and where it cannot get to a ready source of nutrients (that will only allow it to grow shoots and no flowers) do not feed it !!!
Ours was put in and fed with old manure when it was, and did not flower, it did grow and cover much of the wall as we wanted though since then (7 yrs ago), it has been top dressed with old manure once and it flowered and growmored once when the flowers were out (I thought it would do it good,IT DIDNT) all the flowers paled to almost wite and fell in a matter of days. It has recovered since and we donot feed it at all and it flowers freely every year, this year it has had a "second "flush , dribs and drabs of flowers appering at the very top in 2s and 3s.
Hope this helps ,if planted somewhere free draining then try regularly flushing copiously with water to wash the nutrients out of the soil but don't let it be waterlogged.

They often do best against walls where there is a lot of builders rubble etc in the ground promoting drainage!

Good advice too Indypendant.

The fact that it is a Legume and has nitrogen fixing bacteria on it's roots also means don't feed it as Indy says.