Clematis are pretty much trouble free, suffering from just one serious problem known as 'Wilt'. Suddenly, with no warning, all the plant, or sometimes just a part of it, collapses and 'dies' - generally just as the plant was about to flower. It looks as though someone has cut through the stem at the bottom and it can strike literally overnight. Caused by a fungus called 'Ascochyta clematidina' which is present in everyone's garden, (so it's not your fault - or ours for that matter) it enters the plant via a damaged stem or leaf.
Cut off and burn all the affected parts, down to ground level if necessary and drench the remaining plant the the earth around with a systemic fungicide, carefully following the manufacturers instructions. THIS IS WHY YOU PLANT DEEP. Get those leaf nodes down - they will produce new shoots from under the ground and act as your insurance policy, not just against wilt, but all the other terrible things that can happen to slender stemmed clematis - strimmers, hoes, footballs, dogs, builders, jobbing gardeners etc.
It has to be said that not all plants that appear to have Wilt actually do. Often a slug has eaten through the stem, or it has been snapped in some way, giving the impression that the problem is more serious than it is. We have found that plants in their first year of growth can be affected more frequently than established specimens and also plants in high water areas seem to be less affected than those in drier areas. Paying attention to watering is, therefore, a part of the solution.
Planting well in order to encourage strong plants is also extremely important. A healthy strong plant is a disease resistant plant. Wilt mainly affects the large flowered hybrids, especially the earlier ones, so if you have found this to be a discouraging problem, grow the species varieties instead which, although not wilt-proof are certainly wilt resistant to a remarkable degree.
Mainly affects montana varieties. A yellowish substance leaks out from the base of the plant generally after a hard frost. It would seem that when the sap is rising and a sharp frost occurs, the stems burst much in the same way as a pipe. It can kill large old specimens. Cut back growth to below the affected part to ground level if necessary. New shoots may grow from below the ground. Best thing it to wrap the stems of your montana's with fleece, or even an old blanket to protect against those late frosts.
In particularly humid summers texensis and herbaceous varieties can acquire a dusting of mildew - spray with fungicide if necessary. Planting them where air can circulate freely helps too.
What is eating your clematis flowers? Probably earwigs, creeping out at night (have you noticed how much damage is done at night?) Was that really clematis wilt - or slug/snail damage? These are not really major problems and they are certainly no more than any other plant suffers from. It's a case of living with the enemy and to a large extent controllable. Doubtless you have evolved your own methods.
Do protect new emerging shoots as they must be particularly tasty - mice and slugs love 'em. Some people have thought their plants have died during the winter, or that they have never produced new shoots after being cut back after suffering from wilt. Alas, the new shoots are struggling to come up, but are being eaten off the instant they appear. Making a plastic collar from an old lemonade bottle is not a bad idea - it can be removed when there is enough woody growth.
Vine weevils cause havoc in gardens, most especially to plants in containers. They are beetle larvae, a creamy colour with a dark head, fat and 'C' shaped and they eat the roots of plants. Certain things are especial favourites (Heuchera's, Ivies, Primula's) and fortunately clematis are not in that category. However, they can and do damage clematis, especially those in containers, and wherever possible preventative measures should be put in place. Using a compost which has added chemicals to deal with the larvae helps somewhat, but they are by no means as successful as the manufacturers would have you believe. Likewise control by biological methods is only truly successful in greenhouse/conservatory environments and is also very expensive. If your plant looks miserable for no apparent reason it is worth checking for these menaces especially if it is in a container. Of course we, at the nursery, do all we can to make sure the plants are bug-free. However, we find commercial preventatives are only about 60% effective and adding old fashioned methods (try flea-powder in your compost), noxious smelling but 'green' sprays and sacrificial crops (Mother of Thousands) cannot guarantee immunity.
Fast multiplying sap-sucking insects which cause stunted growth. Use systemic insecticide against them and keep the plant well watered (dryness increases the problem).
Getting harder and harder to control as they have developed increased resistance to sprays. Parasitic wasps are a 'green' alternative.
Not a serious life-threatening problem unless completely out of hand! The larvae tunnels through the leaf leaving a lacy effect. Nip the leaves off and burn them.
at the base of the plant: These were the first leaves to appear, so are now the first leaves to die. It is a natural occurrence - hiding this deficiency with a shorter growing plant is probably the best option.
Caused by magnesium deficiency - a good dose of Epsom Salts is the cure. Yellow leaves and little growth can also be caused by too much water. Either water less or check that the site isn't a bog and move the plant if necessary. Don't forget that the majority of clematis look like dead sticks in the winter, and they prepare for this metamorphosis in the normal fashion during the autumn.
Happens mostly with white and paler coloured varieties after especially cold weather and can look very unusual and attractive in its own right. Direct sunlight will help the flower develop properly along with a dose of Sulphate of Potash, though proper regular feeding should minimise the problem anyway. (Duchess of Edinburgh and Alba Luxurians are supposed to have green in them).
Sometimes, although a clematis has made lots of growth and looks perfectly healthy, it produces no flowers. This could be due to overfeeding (too much is just as bad as too little), or pruning at the wrong time - for instance, a montana pruned back in winter will have no flowers. An early flowering hybrid that has been hard pruned will also flower later than it should - and a hard winter will prune your plants for you, like it or not, and this will also affect their flowering capacity. Finally, awkward plants that they are, your clematis could just have decided to have a year off!
This article was originally published on the web at ukclematis.co.uk, however that website is defunct at January 2009. The copyright is with the original owners of ukclematis.co.uk.