You need a Wisteria 

For anyone who visits my garden center in late April to mid May, they can’t help but notice the two wisteria vines I have growing over an arbor that frames the entrance to our perennial department.  They have been planted there for at least 5-6 years (probably more like 8-10) and have never failed to be absolutely covered with masses of fragrant blooms every spring.  It is a sight to behold and a wonderful smell to enjoy.  It is quite frankly most impressive if I do say so myself.

As I talk with customers I think what makes this wisteria arbor so eye catching is that one, it is a total mass of flowers and two, it is very well contained.  None of this happens by accident.  Proper pruning and choosing the right varieties are what makes it all work. 

So let’s talk a bit about Wisteria varieties first.  Wisteria is native to the Eastern US and Korea, China and Japan, however most of the popular varieties hail from either Japan or China.  All are completely hardy for our northwest climate and grow quite vigorously once established.  Due to many years of hybridizing it can be difficult to tell the species apart but there is one little trick that usually lets you know if you are looking at a Chinese variety (sinensis) or a Japanese variety (floribunda).  Chinese plants will twine counter-clockwise and Japanese ones will twine clockwise.  I have to confess that in all the years I have gardened I have never bothered to see which way my wisteria is twining but if you are interested then now you know how to tell the difference.

Recently, I was reading my wife’s THE ENGLISH GARDEN magazine and came across an article about a garden in Pyrford Court, Surrey where there is growing the National Plant Collection of Wisteria.  Contained in this garden are no less than 38 cultivars of wisteria.  I can just imagine how intoxicating it must be this time of year to wander the grounds of this garden.  But 38 varieties could make one’s head spin.  Fortunately, you will never find that kind of selection in our Puget Sound nurseries.  At most you might come across a dozen or so and even then many of them will be hard to tell apart.  Over the years we have winnowed the choices down to four or five; a good purple, white or pink, maybe a double flavor and this year one called Kyushaku that when mature has flower racemes in excess of 6 feet long.  Now that’s impressive!

The majority of wisteria that is sold in local garden centers is grown in California by a wholesale nursery called L.E. Cooke.  What makes their wisteria so special is that they graft their varieties onto a seedling rootstock.  Doing this allows their plants to come into bloom in the first few seasons rather than taking several years which is what happens with seedling grown plants.  If you have a wisteria that has never bloomed then chances are that it is a seedling variety and has yet to reach maturity.  Your only option is to embark on a vigorous pruning program which if you are lucky will bring it into bloom.

So now let’s talk about pruning.  The secret to getting wisteria to bloom is in the pruning.  Once it is established, you will need to do a summer pruning followed by a winter pruning or else all you will have is a huge tangle of vine and only scattered blooms.  Here’s how you do it.

In the summer, (which is July and August for us), you need to cut back all the twiggy growth to within 6-12 inches of the main stems (look for 5-6 buds).  This will keep the vine within bounds and start the process of setting buds for spring.  It is always okay to do “light” pruning anytime but this summer pruning must be done if you expect to have lots of flowers the following spring.  It may take two seasons before you start reaping the rewards of this regime.  For the rest of the summer you can let your wisteria grow.

In the winter, preferably late February or early March you will again go in and shorten all the twiggy growth.  Only this time you need to cut it back to within 3-6 inches of the main stems (look for 2-3 buds).  Those 3-6 inch stubs that you have left are where the flowers will develop for spring.  This is an aggressive pruning program that may seem extreme if you don’t understand the value of it.  In the end though, you will have a mass of blooms on a very tidy vine, just like the two plants that flank the entrance into our perennial area.