Most varieties of Clematis are known to suffer from Clematis Wilt. It is usually a fatal disease of Clematis. However, there are several precautions that can be taken to make sure that you clematis has the best chance of survival and also steps you can take to prevent Clematis Wilt.
It is not as common as was once the case, for Clematis sold in garden centres are generally much healthier than was the case several years ago.
Clematis Wilt, is not the only cause of Clematis suddenly wilting and dying from the top down. Clematis can soon wilt with disastrous consequences simply from slug or other damage to the lower stems. Sometimes it is the whole plant, sometimes just a few stems.
True Clematis Wilt is a fungal disease (Phoma Clematidina) which can find its way into the plant - after stem damage by other causes. It is very quick to take hold, and a seemingly healthy plant one day, can turn into a drooping specimen the next - thereafter with the foliage dying off and a quick descent into death! Quick action by way of cutting out all of the affected stems, and burn them immediately. If this means cutting the Clematis right down to ground level or just above - so be it. The plant will normally respond to this drastic action. It can further be helped with an application of Tomato Feed - or any other general fertilizer.
Clematis Wilt can happen quite soon after initial planting - as a result of some damage or other in the handling of the plant prior to, or at the time of planting. So, care in transportation is quite important - as is care when planting not to damage any stem tissue. (When trying to unravel plants at a garden centre, always make sure to hold the pot, and not simply pick the plant up by its cane and/or stems. Care is also needed with established plants - especially when forking around or near an established Clematis. Firm support to stop the plant rocking about in the wind is another measure that can be taken to try to avoid this disease.
When you initially plant your Clematis, make sure that you plant it 4-6in (100-150mm) deeper than the soil level in the pot. If an attack of wilt then takes place at sometime in the future, there is a good chance of the Clematis shooting up from new buds just under the soil.