The Q&A Archives: Established Wisteria Without Flowers

Question: I bought my Wisteria from a local reputable nursery about
ten years ago. It is trained into a tree and has anywhere
from two to twelve flowers each Spring, max. It is in full sun, and I have tried to withhold fertilizer and excess water, all to no avail. I am so discouraged. The plant is very healthy and grows like crazy. I prune twice a year. After researching your site, I have decided to root prune as my last resort. Should I just continue to be patient and it will bloom eventually, or should I cut it down and start over?

Answer: I know how disappointing it is when wisteria won't bloom. It sounds as though you've done a lot of research and are following the suggestions - with the possible exception of pruning twice a year. Here's why I'm concerned: There are actually three different species of vining wisteria that have similar blooms: Japanese wisteria is Wisteria floribunda, Chinese wisteria is Wisteria sinensis and American wisteria is Wisteria frutescens. The most commonly grown plant is the Japanese wisteria. All three of the plants are prolific vine producers and can grow thirty feet or more. Japanese wisteria is more invasive than the others. If you wanted to extend the bloom period, you could plant all three, since the Japanese variety blooms first--typically April, while the Chinese blooms in May and the American variety blooms June to August on the current season's growth. For that reason, you need to prune at the correct time for the type of wisteria you're growing. The oriental varieties set their flower buds in the fall for spring bloom and should be pruned after flowering. The American variety should be pruned hard before growth begins. All will perform best in full sunlight, and need little in the way of nitrogen, since rapid growth can preclude flowers.

Wisteria can take up to 8 years to begin blooming if it is grown from seed. Age is probably not a factor with your plant. Nitrogen fertilizer or rich soil can also produce foliage growth to the exclusion of flowers. Try avoiding nitrogen around it, and apply some super phosphate instead. You can certainly try root pruning; it sometimes stresses a plant just enough to convince it to bloom. In this case, I hope so!

Best wishes with your wisteria!

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