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Let’S Take Another Look At Some Ideas To Get A Non-Blooming Wisteria To Flower For You
by Art Drysdale
by Art Drysdale

email: art@artdrysdale.com

Art Drysdale, a life-long resident of Toronto and a horticulturist well known all across Canada, is now a resident of Parksville, British Columbia on Vancouver Island, just north of Nanaimo. He has reno-vated an old home and has a new garden there. His radio gardening vignettes are heard in south-western Ontario over radio station Easy 101 FM out of Tillsonburg at 2 PM weekdays.

Art also has his own website at http://www.artdrysdale.com


August 2, 2015

Above, our Wisteria growing on the east-facing side of our home in Toronto. Below a huge white-flowering Wisteria. Author photos.


 



 

For those of you awaiting the second ‘chapter’ in the story of the CNIB Fragrant Garden, begun four weeks ago, again this week I failed to get all of the additional information I was hoping to get, and so that second `chapter` is having to be put off yet again. Sorry about that, hopefully I’ll get lucky next week!

In the early spring, there are always a lot of questions about Wisteria vines (or trees) that don't bloom, but produce lots of foliage. We used to attribute this to a lack of hardiness of the flower buds, but more often now it seems the problem can be corrected with proper pruning. Now in a short item, I cannot pretend to give you all the information you need to make a wisteria flower. But I will give you some of the suggestions that have worked for me, and which by the way, originally came from Laura Grant, executive director of the American Rhododendron Society.

First and foremost, the pruning really begins NOW, not in the early spring, although some is necessary then as well. The pruning regimen presented here assumes the vine has reached the maximum height at which you would like to keep it. If not, commence this regimen only once the vine has reached your desired height.

Right now, you should prune off all of those young thin shoots, often a metre long, that the vine produces from all major growths. Prune them all back to about 5-7 cm (2-3") of the larger growths from whence they emerge. Leave only one or two leaves adjacent to the major branch on each. You will find that you'll have to do that several times this summer, as a healthy, vigorous plant will keep producing these shoots. Just keep cutting them back close to the main growth throughout the summer!

By doing this pruning on an ongoing basis, you will considerably lessen the rampant growth of your wisteria vine, and simplify the pruning that needs to be done in late winter/early spring.

The spring pruning entails the same principles. All thin growths are shortened back to within a few buds of the major branch. In the spring each cut must be made judiciously, being careful to look for the conspicuous flower buds (as different from leaf buds). Depending on how early in the season this pruning is done, the flower buds will appear as tiny acorns on the branches. Each thin branch should be cut just a little past the flower buds, leaving the flower buds just a few centimetres in from the cut.

Now, there once was a book written in Britain that contained 1,000 suggestions for making a wisteria bloom. A way back, when I was a student at The Niagara Parks Commission Botanical Garden and School of Horticulture, I recall 'Bert' Henning, the superintendent (an English horticultural graduate) having us students spend considerable time pruning two giant old wisterias on the wall of "The Bothy"-our residence building. It seemed to me that over the years, we must have exhausted at least half of the 1,000 suggestions in the British book!

Obviously I haven't the space here to outline all of the suggestions made in that book. However, there is one I should mention. Root pruning often will cause stubborn non-flowering shrubs and even trees (including woody vines such as wisteria) to flower. That means digging a trench around the plant (out about 60 to 90 cm [2-3'] from its crown). It needs to be at least 40 cm (16") deep-deeper depending on the number of roots encountered. If the plant is growing against a wall (as ours at the school were) the trench should be all the way around the 'open' side, and possibly as deep as 90 cm (3'). This can be tried every other year for several years.

Finally, there are now two distinct types of Wisteria available here. The oldest plants in Canada are generally Wisteria floribunda, and more recently, Wisteria sinensis became available. The flower clusters on floribunda are generally longer (often 40 cm/16"), and the foliage is a brighter green. The Japanese wisteria (W. sinensis) has shorter flower clusters and is generally considered easier to make flower. Also, by pruning after the initial blooming, the Japanese varieties will often have a second set of blossoms about now in the early summer. In addition to these two major types of Wisteria, many nurseries are now selling an even slightly hardier species: W. macrostachys ‘Blue Moon’. There are many folks in Western Canada who have been able to make this one flower for them.

If you are considering planting a wisteria, then do as I have done—plant two different ones in the same hole. Preferably plant one floribunda and one sinensis. And, do remember it is not necessary for wisteria to be planted against a wall. They easily make an excellent tree with a little training and staking in the first few years. The pruning instructions are the same for tree-like specimens as for the vines.

   

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