Clematis Wilt
This month you may have noticed shriveling of some stems on your clematis, while others of us have been so unlucky as to experience a dramatic demise of the entire plant shriveling and turning black in a week. These symptoms are typical of a disease called clematis wilt.
Cause
These dramatic symptoms most often manifest just as the plant is about to flower, typically striking the flower buds and new growth first. In my research, I have found 2 fungi credited with causing this theatrical demise, Phoma clematidina and Ascochyta clematidina. These pathogens enter the vine’s vascular system and clog the fluid-carrying tubes causing all parts of the plant above the clog to wilt as if it needs water.
The new growth of Clematis 'Piccadilly' shriveled from clematis wilt. photo credit: R. Robert
Treatment
Luckily, this disease does not attack the roots. Simply prune out the affected stems or trim the plant to the ground. New shoots will emerge and some cultivars will bloom again in the same season. Be sure to disinfect your tools after pruning the infected plants to avoid transmitting the disease to other plants.
Once the plant has established heavy, tough stems the problem appears to lessen. In other words, the plant can outgrow the disease. These symptoms have lead some gardeners to call the disease “juvenile wilt disease”.
Clematis addisonii, a small-flowered species. photo credit: R. Maurer
These fungi appear to primarily attack early-season, large-flowering hybrids. If you would like to avoid the trauma of seeing your entire clematis shrivel up and die, plant small-flowered species like Clematis montana, C. macropetala, C. alpine, and C. viticella.
Peter Hickman July 15, 2009 at 10:26 am
Great information for this time of year, when newly planted Clematis are starting to flower. Are there any fungicides that homeowners can apply to prevent this disease or that needed to be applied to prevent reinfection after the diseased tissue has properly pruned off the plant?
Becky Robert July 15, 2009 at 1:03 pm
After pruning disease plants, some references recommend fertilizing and watering your plants well. To prevent return of the disease be sure to sanitize your tools after each cut. Do not compost the infected growth as that will not destroy the fungus.
As preventive measures, sight your plant in an appropriate place and be sure it remains well watered. Avoid creating stress for the plant. Some references recommend a systemic fungicide to be applied in late spring. These treats seem unnecessary because the disease does not cause death of your plant and will re-sprout after removal of infected growth. Once the plant is well established it will out grow the disease.
To avoid the disease all together plant small flowering cultivars, which are resistant.
creid November 5, 2009 at 5:20 pm
Hmmm… you say “plant small-flowered species like…C. macropetala….”
I thought “macro” meant big and “petala”meant petal, referring to large-flowered clematis. I thought the macropetalas were most commonly infected with these fungal diseases.
Please enlighten.
Becky Robert November 9, 2009 at 3:17 pm
You are correct. Macro and petala do imply that C. macropetala is a large flowered clematis. As species clematis, it does have a larger bloom than other species clematis. The clematis most susceptible to wilt are the large flowered hybrids, not the species clematis, which all have smaller blooms than the hybrids.