Posted: 09/09/2017 at 08:38
Did you look at the link above that Obelixx sent? Advice from the RHS, I've copied and pasted it:-
Training as standards
Standard wisterias can be grown either as specimens in a border, or in a large pot.
Start with a young, single-stemmed plant, and insert a 1.2-1.5m (4-5ft) stout support next to it when you plant into the ground or container. This will be used to create the main stem of the ‘lollipop’ If planting in a pot, John Innes No 3 potting compost is a good choice of compost. Make sure the wisteria is planted to the same depth as it was in its pot from the nursery, spreading out the roots and loosening the root ball before planting. Choose a cheap container that is only slightly larger than the plant needs, potting it on gradually as it grows to fill its final display container Train the stem vertically up the support (this is usually stronger than twining) Allow the plant’s leader to grow unchecked until it reaches the top of the support and then remove the tip in the following February to encourage the formation of sideshoots Prune the sideshoots the following winter, shortening them to 15-30cm (6in-1ft) and repeat this process each winter to gradually build up a head Weak or misplaced growth can be cut out entirely, as can older branches if the head becomes too dense in later years As the head develops, prune in August as well. Cut off above the seventh leaf any shoots that are not needed to extend the head The following February cut back these shoots to 2.5cm (1in) of their bases, just as you would routinely prune a wall-trained plant.