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Growing Wisteria

Wisteria puts on the most spectacular display of flowers during springtime in WA and although they originate from Asia, they thrive in our well drained soil and sunshine.  For those lucky enough to have a wisteria already, maintaining them becomes easier as they establish and for those about to plant one, be patient as the heady perfume and pendulous flowers are worth the wait.

Chinese wisteria (Wisteria sinensis) produces an amazing display of fragrant deep violet flowers that hang in masses from stems that twine anti-clockwise around verandah posts, gazebos and pergolas.  It is also available with white flowers (Wisteria sinensis alba) which are only lightly fragrant but make a striking backdrop.  Chinese wisteria is the variety most often grown in WA because it is big, bold and beautiful!

Japanese wisteria (Wisteria floribunda) can be quite varied in both colour and size.  Dwarf varieties are compact and slow growing and form a shrub-like shape which makes it perfect for training as bonsai or into standards.  Larger varieties have very long racemes (up to 40cm long) of pink, white, violet and lilac coloured flowers which hang like pendulums from long stems which twine in a clockwise direction.

Wisterias are very vigorous vines which will quickly scurry up any structure that is available, even into the roof eaves if they can.  They need a very solid frame of timber, metal or thick wire as they become heavy when they are laden with leaves and flowers.

Smaller growing wisterias look amazing in pots and can be trained into standards providing a strong metal pole is used and the pot is wide enough not to blow over from the weight in summer.  Wisterias grown as standards in the garden need to be extremely well braced and care should be taken not to allow them to become too top heavy.

The best location for a wisteria is on a sun-drenched wall or pergola as its branches need the warmth to produce the best blooms.  Grafted wisteria, the type mostly bought in garden centres, can take between 3 to 5 years to begin flowering and seed-grown can take up to 10 years but the superb display is worth the wait.

Sometimes a wisteria will go years without flowering so try to give it a kick-start with a weekly application of liquid fertiliser which is very high in potash from August through to February.  Avoid nitrogen-rich fertilisers as these will encourage a mass of leaves but no flowers.

The timing for pruning wisteria is different to many shrubs and climbers so that the newly forming flowering spurs are not accidentally removed before they get the chance to bloom.  In WA, wisterias are best pruned twice a year.  The main prune is in summer, a few weeks after it has finished flowering, to establish the main framework and thin the vine and the second prune is in autumn.  It’s best not to prune wisteria in winter like other spring flowering shrubs as the flower buds have already formed and these may accidentally be cut off.

In autumn, remove any dead wood that may be coming from the base or within the framework of the plant. Then, stand back and look at the difference between the old, often gnarly wood, and the thinner side shoots that grow from them; you should be able to see a change in colour.  Cut back the side shoots to about 4 leaves or 15cm.  Older branches can also be cut back to about four buds to help their shape.  The wisteria will now put all its efforts into producing lots of flower buds on these shorter stems that are in their second year of growth.

During summer, the same procedure can be followed but the side shoots should be cut back a bit harder to around two leaves from the branch.  Also, the long whippy stems should be cut off unless the aim is to have the wisteria spread.  These will grow fairly quickly and take hold on anything that they find.

The long seed pods can make a wisteria look a bit messy at the beginning of spring.  These can be cut off but don’t remove too much of the stem as this may have some buds which, if left, will flower next spring.

Wisteria can be grown from the seed pods but they may not be identical to the parent plant.  To do this, put the pods in a large paper bag and leave them to dry in a warm spot.  Sue McDougall recommends putting them on the dashboard of the car for a few weeks until the pods burst allowing the seeds to be separated from the pod.  Plant the seeds about 2cm deep in a pot of premium potting mix and put this on a south facing wall so that it gets a bit of shade.  Once it’s germinated, it can be moved into more sun.

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