Pruning Wisteria

Wisterias are some of the most magnificent climbing plants and a well grown flowering specimen, properly pruned is a sight to behold. In my younger days, I worked on a retail nursery and one of the staff would never sell a customer a Wisteria without providing them with a hand drawn diagram on how to prune it. 

If you are considering growing Wisteria, choose a sunny south or west facing wall or alternatively a post or a pergola in a sunny spot. A fertile, well cultivated soil with good drainage is important. Use a general purpose balanced fertiliser (I use blood, fish and bone) for planting and reapply annually. 

I recommend selecting plants that have been grafted. Most reputable nurseries and garden centres will sell these plants in preference to the inferior seed raised plants that may take a long time to flower and may have inferior blooms. Grafted plants will have an easily identifiable graft union at the junction of the rootstock and scion, this will show as a slight bulge. Grafting Wisterias is a skilled job and this makes the plants more expensive than seed raised ones but the difference is well worth paying. 

if the plant is to be grown against a wall, provide a system of support. Wisteria attach themselves to the support by means of twining stems, strong galvanised wire held in place by short, strong eyelets is a good means of providing this support. I much prefer short eyelets as these can not be bent by pulling the wire taut to make a nice, neat job.  

I usually cut back the main stems of a newly planted specimen to encourage branching. The stems need to be carefully trained to to fill the allocated wall space with stems adequately spaced to provide a pleasing effect.   Once the plant has filled its allocated space, it will need to be pruned twice a year to keep it within bounds, have a neat appearance and an excellent floral display. 

In July, new growth that has sprouted from the framework shoots will need to be drastically shortened. I shorten these back to about 20-30 cm (8-12 inches). New growth will have green wood and you should be able to see where the old and new wood meet. Be brave, you will be taking out a lot of growth but allowing light to get into the plant to encourage flower buds. Just a word of caution, look out for any bird's nests and be prepared to sacrifice some flowers for the well-being of wildlife. You can always finish pruning in autumn after the nesting season. 

Strong shoots coming from the base of the plant should be either trained in to make new framework shoots or removed altogether.

In February shorten back these growths to about 10 cm (4 inches). This wil encourage the formation of spectacular trusses of flowers. 

Badly neglected Wisteria can be hard pruned in early summer , they will respond by producing vigorous growth  that can be used to make new framework shoots or shorted to make flowering spurs. It is advisable not to feed Wisterias after hard pruning to prevent excessive growth. 

There is nothing particularly complicated about growing Wisteria, a twice yearly prune will maintain their status as a showpiece in your garden. 

Wisterias respond well to summer and winter pruning