Blue Sapphire – a classic blue sinenis wisteria

I am feeling the love for wisterias. This love does not last 52 weeks of the year, but when they are in flower, you would have to be lacking in all romance not to admire them. This week it is Blue Sapphire that is looking its very best. White Silk and Amethyst are just opening, to be followed by Snow Showers and Pink Ice. Even the very names are romantic and evocative.

If you have your wisteria beautifully trained and tied in across your verandah (best with an equally romantic looking old villa or cottage) where its long racemes of fragrant flowers festoon down, so much the better. All you need is the rocking chair with calico cushions to complete the picture. I don’t go there, because I know that in the 49 weeks of the year when it is not flowering, that plant is going to take on triffid-like characteristics and try to split the spouting and drive a wedge between the roof and the ceiling. The oh-so-lovely blue wisteria on the side of our house was eradicated years ago. I was too much of a novice to understand why Mark’s father took it out when it looked so beautiful in flower, but now I understand just how quickly a wayward tendril can leap into a gap in the roof tiles, thicken, harden and bingo, you have a broken tile before you’ve even noticed it got away on you.

One growing season is all it takes. Believe me. I have had the lovely Snow Showers split the plastic spouting immediately outside my office window and I prune thoroughly every year. By autumn, one stem had driven such a wedge between the spouting and the building that something had to give.

Snow Showers – a floribunda selection on our bridge

Growing wisteria takes a bit of work. You need to prune them and to train them and picking a suitable location is important. Currently we grow a couple over a wooden bridge (and they have made an attempt to split the bridge timbers), three up strings on a brick wall where they can do no harm beyond leaping into nearby trees if not supervised closely and the aforementioned one up a wooden wall out my office window. I have two waiting to be planted out and they will be going on freestanding metal frames which will support a canopy over time. A bit of forethought can save a lot of trouble later. Wisterias are not something you can plant and leave. I was once told that the largest plant in the world is a wisteria which has layered and leapt its way along 5km somewhere in China. I have no idea if it deserves the title of the largest plant, but I have little doubt that such a one exists.

There are two main groups of wisterias, the Chinese ones (“sinensis” which just means from China) and the Japanese ones (floribunda). The Chinese ones usually have finer leaves and they flower on bare wood before the spring foliage appears. As a relatively random piece of information, the Chinese ones twine anti clockwise whereas the Japanese ones twine clockwise.

Wisteria White Silk

The floribunda wisterias flower as the new foliage appears but to compensate, they tend to have much longer racemes of flowers. Some can be 50cm or more and, as the plant gains maturity, the flowers just get better. White Silk (or Shiro Kapitan) is an exception with its short, fat racemes but it makes up in flower size and heavy fragrance what it lacks in festooning capacity. There are also North American species and I have yet to discover whether they twine clockwise or anti clockwise. The ones most commonly available on the market here originate from China and Japan. The flowers resemble pea and bean flowers and indeed wisterias are members of the legume family.

The trunks of these vines are borer fodder supreme. If you look at an old wisteria, you are almost certain to find extensive borer damage. They battle on remarkably well for quite a long time, but left untreated, sooner or later sections will die and snap out. It pays not to put all your trust in one central leader or even a central plait of three leaders. Sooner or later, the borer are likely to take them out so you want to be training the occasional replacement through as well.

Whenever you spot a borer hole or borer sawdust, treat it. Either cut it out or pump the hole full of insecticide (fly spray seems to work) or light oil such as a cooking oil. I favour CRC because the spray cans come with those handy little tubes for poking down the hole.

If you are willing to put the work into managing your wisteria, they will reward you in a most gratifying manner.

Wisteria Amethyst

Help! My wisteria won’t flower.
1) Check for borer infestation and make sure the plant is still alive.
2) The sparrows may have disbudded it. Sometimes they develop a taste for the buds but you should see freshly damaged debris lying below.
3) The plant has been pruned incorrectly in winter. If you cut it back to a stump every year, you are cutting off all the flowering spurs. Sort out the main stems and then prune back all the side canes to three or four buds out from the main framework. That is where the flowers develop from.
4) You have bought a seedling instead of a named variety. Replace it.
5) You have a grafted plant and the root stock has taken over. We much prefer cutting grown wisteria so this problem does not arise. If you can identify what is root stock, remove it to allow the grafted variety to grow without competition. These days, most plants are cutting grown.

First published in the Waikato Times and reprinted here with their permission.