Wisteria problems and what to do about them

Wisteria problems and what to do about them

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Wisteria problems such as graft failure and root diseases such as honey fungus and Phytophthora root rot are either biological (pests and diseases), environmental (sun, location, etc.) or due to your care such as incorrect pruning results in no flowers. In this guide, I share my experience with all of these here and give advice on what to do about each of them.

Specific problems

I’ve already addressed specific problems in Why is my wisteria not blooming? and Why are my wisteria leaves turning yellow or wilting? so if this is your issue, these guides might be helpful for these specific issues.

Biological problems

Pests and diseases

Wisteria Scale Insect and How To Control Them
Scale insect that can attack wisteria and cause wilting leaves

Pests such as scale insects and diseases such as honey fungus affect many plants, including wisteria. The guide Wisteria pests and diseases to watch out for, details the common ones to look out for on your wisteria plant. It also has information about what to do about each pest and disease.

There’s also a detailed guide about the Wisteria scale insect, which is becoming more common and is larger than other scale insects with blackish-brown shells which are 10mm wide. They can also suffer from other scale insects, but there are usually smaller (5mm) and light brown or grey.

Wisteria graft failure

In the guide, Growing Wisteria Amethyst Falls, I recommend buying a wisteria plant that’s been propagated by a cutting or has been grafted from the original plant. Most wisteria is grafted to a rootstock. This is still the advice to follow, but sometimes the grafts have been known to fail – even after many years of strong and healthy performance from your wisteria. I have seen some wisterias where the graphs have actually failed after 20 years.

When this happens, the graft often decays. The graft is usually close to the soil level so look for any problems there. Another easier-to-spot clue to this problem is that new shoots appear from below the ground while the top of the plant dies back. The new shoots are developed by the root stock, not the grafted part of the plant.

What to do

When the root stock has failed, unfortunately, there is nothing you can do but dig up the wisteria plant and replace it with a new plant. The shoots coming from the rootstock are not the original plant.

Environmental problems

Wisteria grown in pots require more watering than those in the ground to prevent watering issues
Wisteria grown in pots require more watering than those in the ground to prevent watering issues

Everything

There are so many things that can be incorrect with the plant’s location, soil, sun and other environmental factors. It’s quicker to read what to do right rather than what not to do.

What to do

To find out the best circumstances to grow wisteria in, it’s well worth reading my guide on Growing Wisteria Amethyst Falls and Growing Wisteria in pots and containers. The quick answer is that they prefer fertilse, well drained soil in a sunny position. They also benefit from pruning twice a year, once in July/August and then again in January/February.

Your care

Healthy wisteria growing up wall that is cared for correctly

Yes, you may do things that cause problems for your wisteria plant without really realising it, this can be from not watering then enough when buds are forming in the previous year to incorrect pruning.

Watering

Both over- and under-watering your wisteria have the same final effect on your plant. The leaves turn yellow and wilt, and finally, fall off. Along the way with over-watering, phytophthora root rot may set in and destroy the very foundation of your plant.

What to do

Only water your wisteria when the top 3cm of soil is dry. Ensure that the excess water is draining away fully and the plant doesn’t become water-logged. When growing them in pots, this means making sure there are drainage holes and they are covered with crockery to stop them from becoming blocked up. If planting in the ground and the soil sometimes becomes waterlogged, dig plenty of horticultural grit and organic material into the ground to improve drainage. Mulch well around the plant (but not too close to the trunk) to help with water retention.

Remember that wisteria grown in pots and those that you grow up a wall dry out quickly and need more frequent watering.

Pruning

Wisteria that is correctly pruned to promote more flowers
Wisteria that is correctly trained on wires and pruned to promote more flowers

Wisteria need some care and attention in deadheading and pruning. Remove the blooms as soon as they’ve faded to encourage new flowers to grow. And make sure to prune the vines twice a year (spring and autumn) to keep the wisteria under control and promote more flowers. A wisteria plant left unattended can create all kinds of problems (see Will wisteria damage my house?) and look unsightly.

How to prune wisteria gives the details of this essential pruning task, if you prune them incorrectly, you can remove the flowering shoots for the following year and get no flowers.


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