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Wisteria by Raymond Neil Macaway

Why Doesn’t My Wisteria Flower?

  • Age
  • Pruning
  • Sunlight
  • Fertilising
  • Potting
  • Watering

We will look at each of these topics and see how this information can help to achieve a
healthy Wisteria.
It is important to mention that I live in Sydney; therefore, any mention of seasons is
relative to this climate.

Seasons in Sydney

  • Summer: December to February
  • Autumn: March to May
  • Winter: June to August
  • Spring: September to November


  • Seed: If the tree is from seed, it can take 7 to 15 years for the tree to be mature enough to flower.
  • Air Layer: If the layer is taken from a tree, known to flower, it has been my experience that the tree should flower the next year if teh correct maintenance is performed 


  • Pruning is one of the secrets to good flowering.
  • After flowering cut off the flower stems. (See Below).
  • The main prune will be during spring after traditional flowering. You can go all over the tree and cut back to about two branch-lets. If you cut any branches that are larger than half a pencil thickness, seal them.
  • Prune up to the end of January

The tree before pruning. And After

From the end of February to September if you see any rampant whippy growth. Cut them back to three buds.


Wisterias need a lot of sunlight to flower. It is important for the tree to get at least 6 to 8 hours of sunlight a day.


Wisteria needs the right fertiliser to get flowers. If the wrong fertiliser is used it will most probably produce lush foliage, but few flowers.

This is most probably a good time to mention NPK, referred to fertiliser, actually does. This is a brief breakdown of NPK.

  • N – Nitrogen is used by plants for lots of leaf growth and good green colour.
  • P – Phosphorous is used by plants to help form new roots, make seeds, fruit and flowers. It’s also used by plants to help fight disease.
  • K – Potassium helps plants make strong stems and keep growing fast. It’s also used to help fight disease.

Wisterias need phosphorous in the fertiliser. If they get too much Nitrogen it will certainly make them look green but won’t help flowering. Therefore, give them a rich phosphorous fertiliser August and then in February.

I use two fertilisers, Seamungus and Mega Booster Organic Fertiliser. A tonic and soil treatment, Seasol and GoGo Juice. Two liquid fertilisers, Powerfeed and Charlie Carp.

Application of Fertiliser

DANGER WARNING: Please be careful when using fertiliser. Wear a mask. Don’t breathe the dust and wash your hands after use.

Apply a coating of Seamungus on top of the soil and water in.

Apply a coat of Mega Booster Organic Fertiliser. Be careful not to put too much on. Water in.

This is what the Mega Booster Phosphorus Organic Fertiliser looks like. 

Note: this fertiliser comes in a plastic bag. I empty it into a container with a sealed lid.

Let the water drain for half an hour and give the tree a drink of Seasol mixed with GoGo Juice. Use the following mix per litre of water: 3ml of Seasol and 4ml of GoGo Juice.

Give the tree a dose of fertiliser in August and another in February.

Additional Fertiliser

When to use the liquid fertilisers

  • In October give teh tree a drink of Powerfeed.
  • In December, April and June give the tree a drink of Charlie Carp.

Fertilising after Re-potting

  • If you re-pot in January, November/December, (See re-potting below), use Seasol and GoGo Juice for a couple of weeks, twice a week. After the two weeks, give the tree a drink of Powerfeed. Now, feed the tree with Charlie Carp, every two weeks until February then apply the seamungus and Mega Booster Phosphorous Organic Fertiliser as described above.
  • If you repot in MArch/April, (See re-potting below). use Seasol and GoGo Juice for a couple of weeks, twice a week. After two weeks, give the tree a drink of Powerfeed. Now, feed the tree with Charlie Carp, every two weeks until August then apply the Seamungus and Mega Booster Phosphorous Organic Fertiliser as described above.


It is important not to over pot Wisteria. They like to be somewhat root bound. The amount of flowers are proportional to the roots.

  • Use the smallest pot you can to pot the tree.
  • Only repot when the tree is very pot bound.

Soil – The soil needs to drain well but not be too an open mix. I use a mix from Ray Nesci Bonsai Nursery and add some Zeolite to the mix. In half a bag of Ray’s mix I put 1 litre of Zeolite. I use a measuring jug and fill in to the 1 litre mark of Zeolite, then mix this into Ray’s mix.


  • January
  • March/April
  • November/December


Wisterias area thirsty tree. Make sure they are well watered. During the summer you may find using a water tray will help. If the tree will drink a half filled water tray each day, you know that the extra water is necessary and not doing any harm to the tree.

Does it work?

Have a look at the photo of the pruned tree above , the photo shows what the tree looked like after pruning. The photo was taken on the 29th November 2017

The photo below was taken on the 14th December 2017. This growth developed in 15 days!

The following photos show the tree before the last cut back before leaving the tree to develop ready for flowering. The cut back was done 21st February 2018.

Note how the rampant whippy growth has grown back up itself. This whippy attach to anything it can get a grip on.

During December/January the tree put out several flowers. These flowers won’t be the same size as the flowers during the normal flowering season.

This is what the tree looks like after it’s cut back.

The only cutting back now is to control any rampant whippy growth. The following photo shows how far to cut back. Leave several buds.

In Flower

The trees are Air Layered. The trees flowered after the layers were removed and potted.

The following two photos show the final results

Publication #RNM0009 September 2018
Wisteria Maintenance
Revision 04
Written by
Raymond Neil Mackaway