Pruning Wisteria

First of all, is it a Chinese, Japanese, or American wisteria?

Which way do tendrils twine? To decide this, look at the vine from ground to tip. Check as if you were looking up the vine.

• Clockwise? Chinese (Wisteria sinensis) or American (Wisteria frutescens)
• Counter-clockwise? Japanese (Wisteria floribunda)
• 
  

(There are other species as well to make this trickier)

Number of leaflets on leaves?

• Leaflets 13-19 (Chinese)
• Leaflets 7-13 (Japanese)

Does it matter for pruning? Not sure!

Pruning

• Prune when dormant

Sunset's recommendations:

Late winter

• Once the vine has developed its structure, cut back side shoots to two or three buds (count from where shoot originates). Shorten the flower-producing spurs that grow from side shoots to just beyond the last flower bud (flower buds are fatter than leaf buds).
• Thin any excess shoots by cutting them back to the main stem.
• Cut back the growing tips to limit length.
• Remove seed pods.
• Watch video from RHS

Summer

• Cut long, whippy shoots back to three leaves. Do not cut shoots that are needed to extend the vine or fill in gaps. See video from RHS. Some recommend cutting to 5-6 in summer and then 2-3 in winter.

Supporting Wisteria
They are not self-supporting and must have support. However you can create a tree that will eventually support itself.

Watering
Water if they droop

Fertilize
Don't! They are a legume and have nitrogen fixing bacteria in root nodules.

Why doesn't it bloom?

• Buy a grafted plant on Chinese rootstock
• Not enough sun
• Too much fertilizer and water (use 0-20-0)
• incorrect pH (needs 6-7 pH)
• faulty pruning (don't prune in winter or spring which causes vegetative growth)
• too many suckers

Examples of supports

Japanese Garden in Golden Gate Park

Gamble Garden in Palo Alto

They have a lawn area surrounded by wisteria "trees". The vines are held up with bamboo stakes.
But how are they propped? Is there padding on the bamboo?


References

• Best book according to Pete C:
  'Wisterias, A Comprehensive Guide' by Peter Valder, Timber Press, Portland, OR, 1995
• Difference between Japanese and Chinese Wisteria
• Fine Gardening "Since wisteria flowers develop on the previous year’s growth, pruning wisterias biannually not only keeps these vigorous vines to a manageable size but also creates a system of short branches close to the structure, where you can more easily enjoy the blooms."
• Choosing a Wisteria - Sunset
• Creating a wisteria tree
• SFGate
• Wikipedia
• Name that Plant
• Filoli
• Thompson and Morgan