Common Disease Problems
Bacterial Wilt: This causes yellow streaking on the foliage. It is soil borne and spread by flea beetles. Burpee Recommends: Control flea beetles.
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering, make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Clematis Wilt: This is a stem rot/leaf spot disease caused by a fungus. The stem suddenly collapses, often just when the flower buds are about to open. The leaves and stem turn black and leaf veins may have a purple coloration. Larger flowered varieties tend to be more susceptible than small flowered varieties. Burpee Recommends: This disease may not affect the entire plant, and sometimes the plants recover in a year or two. Make sure your plants are well sited, with 6 hours of sun, cool roots and a well-drained soil and good air circulation. Remove plant debris and avoid injuring the stems and roots. Remove diseased stems immediately.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Rust: A number of fungus diseases that cause rust colored spots on foliage and stalks. Burpee Recommends: Plant resistant varieties. Remove infected plants. Contact your Cooperative Extension Service for recommendations.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Flea Beetles: These small hopping beetles feed on plant foliage and may spread diseases. Burpee Recommends: Use floating row covers to prevent damage to young foliage. Contact your Cooperative Extension Service for recommendations.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Thrips: Thrips are tiny needle-thin insects that are black or straw colored. They suck the juices of plants and attack flower petals, leaves and stems. The plant will have a stippling, discolored flecking or silvering of the leaf surface. Thrips can spread many diseases from plant to plant. Burpee Recommends: Many thrips may be repelled by sheets of aluminum foil spread between rows of plants. Remove weeds from the bed and remove debris from the bed after frost. Check with your Cooperative Extension Service for pest controls.
Whitefly: These are small white flying insects that often rise up in a cloud when plants are disturbed or brushed against. Burpee Recommends: They are difficult to control without chemicals. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for pesticide recommendations.
How do I know when to prune my clematis? When to prune depends on the variety, and if it blooms on new or old wood. In general, vigorous species and early-flowering hybrids do not require pruning, just remove tangled growth. Large-flowered hybrids blooming in early summer on the previous season’s growth can be pruned lightly in the dormant season for structure. Late-flowering hybrids which bloom on current season’s growth can be pruned back to a pair of buds in the dormant season. You can always look up your variety name to see which group it belongs to.
Can I grow clematis in a container? Yes, some smaller varieties may be grown in containers, but not the more vigorous varieties. Be sure that the roots are shaded as they are more exposed in a container.
Will clematis damage the shrubs it climbs over? No, clematis is not a heavy vine such as wisteria and the weight will not damage shrubs. If there is a lot of foliage try to spread it out so it doesn’t completely block the foliage of the shrub.
Is clematis deer resistant? In general clematis is not deer resistant.
Why is my clematis not blooming? Clematis needs a moisture-retentive but well-drained soil, the roots need to be cool but the top needs sun to grow and bloom well. Make sure it is not over fertilized, and not competing with weeds for water and nutrients. Pruning at the wrong season may also prevent blooms.