Wisteria problems: frequently asked questions

Wisteria is one of the quintessential cottage garden plants, with a chocolate-box image of spectacular blooms adorning the front of a country cottage. It is actually a very versatile plant and lends itself to a variety of situations, including growth in containers. Of the few problems affecting the plant, non-flowering and sudden dieback are probably the most frustrating.

Here we give answers to many of the common problems encountered. They are grouped by the area of the plant affected: shoots; leaves and flowers.

Wisteria growing over house wall.

Quick facts

Most common problems

  • Non-flowering
  • Powdery mildew
  • Scale insects
  • Graft failure
  • Honey fungus

Problem gallery

Take a look at some of the common problems you might encounter on wisteria.

Graft failure on wisteria. This young plant failed - the union between roots and the grafted cultivar has broken down. A clue to graft failure is the production of new shoots from below ground level – these are being produced by the rootstock.
Graft failure. While this problem is commonest on young plants, it has also been found on mature plants (some have been reported to be 20 years old or more).
Wisteria scale is a relatively new pest in Britain, which was first found in a London garden in 2001. Since then it has spread further but remains mainly a pest of London and the suburbs.
Symptoms consistent with virus, such as wisteria mosaic vein virus.
Powdery mildew (<EM>Erysiphe alphitoides</EM>) on <EM>Wisteria sinensis</EM>. Irregular dark brown marks and blotches, usually with a yellow margin, are a symptom of infection by the fungal disease powdery mildew.
Phytophthora (Phytophthora species) on wisteria. This is a root rot favoured by wet soils.
    Graft failure on wisteria. This young plant failed - the union between roots and the grafted cultivar has broken down. A clue to graft failure is the production of new shoots from below ground level – these are being produced by the rootstock. Graft failure. While this problem is commonest on young plants, it has also been found on mature plants (some have been reported to be 20 years old or more). Wisteria scale is a relatively new pest in Britain, which was first found in a London garden in 2001. Since then it has spread further but remains mainly a pest of London and the suburbs. Symptoms consistent with virus, such as wisteria mosaic vein virus. Powdery mildew (Erysiphe alphitoides) on Wisteria sinensis. Irregular dark brown marks and blotches, usually with a yellow margin, are a symptom of infection by the fungal disease powdery mildew. Phytophthora (Phytophthora species) on wisteria. This is a root rot favoured by wet soils.

    Shoots

    Question: After many years of healthy growth, the shoots of my wisteria are suddenly wilting and dying. What has gone wrong?

    There are a number of possible causes for this symptom.

    All of these problems prevent adequate water uptake through the roots, leading to wilting and die-back.

    • Wisteria also appears prone to graft failure, sometimes after many years of satisfactory growth. When this happens the graft union (usually close to soil level) often decays, although this is a secondary symptom. A clue to graft failure is the production of new shoots from below ground level, while the top part has died back – these are being produced by the rootstock.
    • If the dead branches have numerous pinhead-sized, raised, coral-pink pustules on the surface then coral spot is involved. However, this disease often attacks plants already weakened or dying back due to other problems.
    • Finally, a severe attack by wisteria scale (see below) can weaken the plant enough to cause some dieback.

    Question: The bark of my plant has numerous brown, limpet-like structures on it. What are they?

    These are scale insects, of which a number of different species can affect wisteria. Found most commonly is brown scale. In south-east England a much larger blackish brown scale, wisteria scale, may sometimes be found. Heavy infestations of the latter scale can lead to branch dieback.

     

    Leaves

    Question: What is causing the brown blotches on the leaves of my plant?

    Irregular dark brown marks and blotches, usually with a yellow margin, are a symptom of infection by the fungal disease powdery mildew. On most types of plant this disease produces conspicuous white fungal growth on the leaves, but on wisteria it can be very difficult to see any growth at all on the blotches (without using a microscope).

    The disease produces another atypical symptom when it first develops on the leaves in early summer – a pale green or yellowish mottling, which can be mistaken for virus infection. Wisteria can also be affected by viruses so if the problem does not respond to mildew controls and persists from year to year, virus may be involved.

    Flowers

    Question: Why won’t my wisteria flower?

    There are a number of possibilities here.

    • If your plant has been grown from seed, it can take up to twenty years to flower, and even then the results may be disappointing! A named cultivar should be more successful, particularly if it is already flowering when it is bought. However, do not be alarmed if such a plant is reluctant to flower in the first year or two after planting. This is perfectly normal and the plant will settle back into flowering once the roots are established.
    • The flower buds on wisteria, like those of many spring-flowering plants, start to develop in late summer of the previous year. Adverse conditions, particularly dry soil, occurring between July and September can cause the buds to abort. Ensure that your plant has an adequate supply of water during this critical period.
    • Sharp spring frosts can cause flower buds to drop before opening, or result in distorted flowers. Other possible causes for poor flowering are too much shade, or inadequate levels of potassium. On poor soils it may be worth applying sulphate of potash in spring at 20g per square metre.

    Regular and timely pruning can help to increase the flowering potential of the plant by producing a framework of flower spurs. In contrast, heavy pruning or pruning in early summer will disrupt successful flowering.

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    • V Maltby

      By V Maltby on 11/06/2014

      Hi - can anyone advise about a sickly looking Wisteria that used to be spectacular. This year the blooms were diminished. The leaf cover is much diminished and there are multiple shoots which appear to have died and which break off easily - the shoots being dry and brittle. The leaves are both smaller and many have dark brown spots on them - some of which have pierced the leaf. These spots are surrounded by a yellow'y halo. Can anyone suggest anything as I fear the plant might be dying. Thank you in anticipation.


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    • Mittens

      By Mittens on 14/06/2014

      Hello, I have just bought and potted two Bredon Springs Tree Mallows to keep on my patio. One is doing very well and seems happy with lots of healthy flowers. The other however, although covered in buds when I bought it does not seem very happy, flowers seem like they are trying to open but appear to be dying before they even get the chance. The rest of the plant looks healthy otherwise. I'm a pretty novice gardener so any suggestions as to why this plant in particular is so unwell would be greatly appreciated.


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    • Scotty1

      By Scotty1 on 26/06/2014

      My Wisteria has same problem as posted on 11th June by member. It flowered as usual, now all the old wood has died and can easily be broken off , the only bits with leaves on at the moment are the new shoots and these leaves are in good condition, no obvious signs of any disease on leaves, stem etc. plant is a well established one covering a wall and roof. It's a real shame. Had anyone got any ideas


    • moll

      By moll on 23/01/2015

      My wisteria is approx. 15 years old. After several years I have now learned to prune at the right time and every year I have loads of flower buds which are then eaten by small striped shell snails! I go out every night at dusk and in the dark with a flashlight to pick off the snails and destroy them. I have tried all the usual deterrents for snails and have sprayed them with Provado but this did not help at all. Every year I have big fat buds then my heart sinks to see that they are being eaten away despite my best efforts. The snails do not eat the leaves! Any advice would be greatly appreciated.


    • Mrs D Berger

      By Mrs D Berger on 16/05/2015

      In 1991 I planted a white Wisteria. It took 5 years to flower and from then on it produced a spectacular display of white flowers, some over a foot long. Two years ago, I noticed one shoot having blue flowers. I cut off the shoot, but last year there were two branches, which I again cut off. This year the whole plant turned insipid blue. How can I get it back to white? Any advice would be greatly appreciated.


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    • Mrs D Berger

      By Mrs D Berger on 16/05/2015

      In 1991 I planted a white Wisteria. It took 5 years to flower and from then on it produced a spectacular display of white flowers, some over a foot long. Two years ago, I noticed one shoot having blue flowers. I cut off the shoot, but last year there were two branches, which I again cut off. This year the whole plant turned insipid blue. How can I get it back to white? Any advice would be greatly appreciated.


    • TedtheJackRussell

      By TedtheJackRussell on 07/08/2015

      I bought my husband a Wisteria for his 40th birthday. He will be 70 next year. The plant always appears healthy but to date we have never had a single flower.!


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