Clematis problems: frequently asked questions
Clematis is one of the most popular climbing plants, its showy flowers giving an eye-catching display. It is usually an easy plant to grow, but can have an aura of mystery surrounding two items in particular: first, when and how to prune the plant, and second, a problem of shoots wilting and dying back. There are also a few other problems to look out for.
- Powdery mildew
- Capsid bugs
Some of the shoots on my clematis are wilting at the tips, shrivelling and dying back. What has caused this?
There are a number of possibilities for this type of symptom, and a bit of detective work may be necessary to establish the cause.
The plant can suffer from root diseases such as honey fungus and Phytophthora root rot. Waterlogging can also cause root decay, in both soil- and container-grown plants. Plants that have been overpotted (i.e. potted into too large a container) are most at risk of wet, rotten roots. Roots of container plants are also vulnerable to damage from vine weevil grubs. All of these problems prevent adequate water uptake through the roots, leading to wilting.
Unsuitable growing conditions, particularly hot, dry soil, will often result in a weak, unhappy plant that wilts and dies back. Physical damage to the stems (e.g. from strong winds or rough handling during tying in of shoots) is also sometimes involved.
If your plant is a large-flowered hybrid, then the fungal disease clematis wilt could be involved. This disease is often first to be blamed, but it can be seen from the above that many cases of wilting clematis are not caused by clematis wilt! Many of the species clematis are resistant to this disease.
One of the stems of my plant has died and is producing a foul-smelling ooze. What is this?
Your plant is affected by a problem known as clematis slime flux, caused when bacteria enter the stem via damage.
What is the greyish-white growth present on the leaves of my plant?
Your clematis is affected by the fungal disease powdery mildew.
What has caused the holes in the leaves of my clematis?
A number of insects will feed on clematis leaves and damage them, including earwigs and the caterpillars of various moths. If the young leaves appear distorted or torn and are full of small, brown-edged holes then the likely culprits may be capsid bugs. Slugs and snails also feed on clematis leaves.
What has caused the curled and sticky leaves on my plant?
Why won’t my clematis flower?
The most common cause of this problem is unsuitable growing conditions. Clematis need a moisture retentive but well-drained soil. The roots need to be kept cool and shaded, but growth and flowering will be impaired if the top of the plant is kept in deep shade. Place stones or pebbles around the base of the plant, or carefully position other plants so that only the base of the clematis is shaded.
Pruning certain species and cultivars at the wrong time of year can prevent flowering, by removing the part of the plant from which the flowers would normally be produced.
If the growing position seems suitable and the plant has been pruned correctly but still won’t flower, try an application of sulphate of potash in late winter or early spring.
Why is my plant producing flowers with green petals?
Low temperatures during flower development are often responsible. Pale or white-flowered cultivars are particularly prone to this problem, known as clematis green petal. Normal flowers should be produced as the season progresses and temperatures rise.
If the plant continues to produce green, distorted flowers throughout its flowering period, then a more serious problem known as green flower disease could be involved. This contagious disease is caused by an organism known as a phytoplasma. Affected plants should be destroyed.
The petals of my clematis are being eaten. What is the culprit?
Earwigs are particularly partial to clematis flowers, and are the most likely cause.
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