September Club Meeting: Wisteria
Annalea joined us at our September meeting to share her extensive knowledge and 22 years experience of growing wisteria's. The capacity crowd enjoyed the discussion and had lots of questions for Annalea.
Highlights of the presentation are included below.
The tree in the above photos is a floribunda or Japanese variety.
Propagation by air layer is the preferred method. Grafts can also work. These methods usually produce flowers quickly. Growing from seed is considered a waste of time.
Best growing conditions for wisteria's vary with the climate and experimentation will be required to get the best out of your plants.
At least 6 hours of direct sun a day is needed to get good flower displays.
Soil needs to be well draining and open. No dust.
A variety of fertilisers over the growing season can be beneficial but it is very important that high potassium varieties are used in late summer/early autumn to encourage next season flower growth. Generally use half the strength of the label suggestions.
Pruning whips is usually done when they get to a metre long. Cut back to three buds. Leave the shorter stubs as flowers bud on these.
Defoliation may be another option for wisteria's but Annalea has not tried this option.
Over time, wisteria branches keep extending and will need to be cut back. An air layer opportunity?
Use wire very carefully as branches/trunks can snap easily. Bend over days/weeks and try to twist the branch to strengthen branches.
When styling, be mindful of the size of the flowers. Wisterias tend to have straight trunks so if taking an air layer, get something interesting. Further bending may also be required.
Wounds/cuts can take a long time to heal. Sealing cut branches and large roots is essential. Sharp tools are required.
Air Layers. Best time is end October/early November. Think about the nebari and trunk movement when selecting the air layer location. Often there is a good thick area where branches join. Use hormone powder. Cover with a thick pad ( 50mm?) of wet sphagnum moss. Cover with clear plastic and tie tightly at both ends. Then apply black plastic over the top so you can check the root development without disturbing the roots. Add more water if required. It should take 6 to 7 weeks for roots to develop. Before potting the air layer, remove as much deadwood as possible from under the root ball and seal well. You should get strong feeder root growth in a flat plane. See photo below for an example of root development after one year in the pot.
Repot annually or maybe very two years.
Beware of fungus attack. They can be terminal and it is often very difficult to detect early indications of infection and to treat. The fungus can be contagious so disinfect tools and hands to avoid spreading it to other trees. See the photo of a casualty below.