How to Grow Clematis

Growth Habit: Most clematis are known as strong climbers, but there are selections that grow more bush-like, vining only a few feet. Vining clematis can be aggressive with some climbing 20 feet tall.

Staking: Most clematis don't need staking in the traditional sense, but they do need support. If they don't have a structure for a vining-type clematis to climb on they will stop growing. The vines climb by wrapping their leaf stems around a ½ inch diameter supports such as wire, twine and thin branches from other plants. They will not climb up thicker supports. Even if you have a wall, trellis, arbor, lamp post or fence, you may need to add thinner supports for the vines to climb upon.

Watering: The old adage is clematis likes sunny tops and cool, moist bottoms. Keep the soil consistently moist, but be sure it's well drained or you may encourage wilt disease. Pay special attention to watering the first year. Don't let the soil dry out during a hot summer spell. Once established, clematis are more forgiving of infrequent watering.

Fertilizing: Clematis are heavy feeders. Amend the soil at planting with compost. Each spring add a 1- to 2-inch layer of compost around the base of the vines and a balanced organic fertilizer with a 3-1-2 ratio of nitrogen, phosphorous and potassium. Side dress again in early summer.

Mulching: Clematis should be mulched annually in the spring to keep the soil moist and prevent weed growth. Use an organic mulch, such as bark mulch, but keep it 6 to 12 inches away from the stems to avoid wilt disease.

Trimming & Pruning: Spring and early summer-blooming clematis should be deadheaded after flowering to encourage more blooms to form next year or even later in the summer. Late summer and fall-blooming types don't require deadheading. In fact, the wispy seed heads are an attractive addition to the fall and winter garden.

All vining clematis should be pruned each year. Pruning clematis can be confusing since it depends on the type of clematis you're growing. The first step is to always prune out dead, diseased and broken stems any time during the growing season. Wait until it's clear which stems are alive and dead in spring before pruning.

Prune based upon the bloom time. For clematis varieties that bloom in spring and early summer on old wood (second year), prune after flowering. For varieties that bloom in summer and fall, prune in spring since these varieties bloom on new wood. Spring pruning will stimulate more growth. For large-flowered hybrid varieties, deadhead spent blossoms after the first flush of flowers. A second flush will occur later in the summer.

When pruning new clematis vines, prune back the vine to about 1 foot from the ground to stimulate branching lower on the plant. As it grows in the first year, pinch the growth tips periodically to force more branching. This will eliminate flowers the first year, but create a multi branched plant that will produce more flowers in the future.

For established vines, prune back the vines by 1/3rd at the appropriate time to encourage more growth. Prune back to right above large buds on the stem.

Dividing & Transplanting: Generally, clematis are finicky about any root disturbances. For that reason, only divide or move your clematis if it's a strong grower. Although clematis can be divided in spring before new growth begins, the new plants may take some time to get established. Before transplanting, remove the plant from the trellis. Cut back the tops so each stem has about 3 to 4 buds. Dig up the root systems, divide the roots carefully and replant in a similar location as the mother plant. Treat the new divisions like new transplants and mulch, keep them well watered, and be ready to wait a season or two for strong new growth.

Pests/ Disease: Clematis has very few serious pests and diseases. The biggest problem home gardeners will find with their clematis vine is stem wilt. This occurs when individual stems growing from the ground suddenly wilt and die. Although this problem feels severe, it usually doesn't kill the plant. Simply prune back the wilted stem to the ground. To help prevent this fungal wilt in the future, plant your clematis in well-drained soil where it gets at least 6 hours of sun a day. Also, avoid damaging the stems or roots while working around the plant and avoid piling compost and mulch too close to the crown. This disease mostly effects the large-flowered hybrid clematis. Smaller-flowered species types, such as Clematis viticella, have less problems with fungal wilt.

Clematis may also be attacked by powdery mildew disease. The leaves will turn white, then yellow and drop. To prevent powdery mildew from occurring, try a home remedy consisting of one tablespoon of baking soda, one tablespoon of horticultural oil and one tablespoon of liquid detergent in a gallon of water. Spray when you first see signs of the disease.