Clematis are truly the queen of garden vines. Their spectacular blooms do so many different things from climbing fences, mailboxes and lamp posts to standing alone on a teepee or pergola.
Clematis prefer 5 to 7 hours of sunlight per day in order to flourish (sunlight requirements may vary according to variety, so check before planting). For best results, plant clematis where vining is exposed to the sun and roots are protected.
Mulching is essential because it keeps the plant’s “feet” cool while improving the make-up or the soil. Place a 3-4” layer of mulch or peat moss. Keep the mulch 8” away from the stem the avoid stem rot. Planting perennials around the perimeter for root shading will have a similar effect.
Clematis is a heavy feeder. In the spring, once the buds swell, start feeding with a well-balanced or bloom-boosting fertilizer. Avoid fertilizers heavy in nitrogen.
Clematis require regular watering, especially during the summer months. Keep in mind that if the plant’s base is shaded it will not dry out as quickly.
Clematis need support to grow. This can be achieved in a few different ways such as growing them on an arbor, trellis, onto other shrubs or onto a fence. They will twine naturally but may need help on slick surfaces. Use a garden roping to help clematis find their way.
Clematis are susceptible to a fungus commonly called clematis wilt. Fungi enter the plant via stems and work their way up, cutting off water to the top of the plant. The plant will quickly take on a withered or black-spotted look. To combat this, carefully cut off all of the diseased parts of the vine and disinfect your clippers with bleach between cuts, then dispose of the diseased parts in a sealed plastic bag. The plant should rebound within a few weeks as long as all infected stems are removed since the fungus does not inflict the root system. An application of a sulfur-based fungicide may be used as treatment but is not always necessary. Fungi spread during periods of damp, humid weather via spores and attack stressed or broken branches that are closer to the ground. A good prevention is to thin out old wood and clean surface mulch yearly.
Pruning for established clematis is divided into three and a half categories based on how the plant flowers:
Group A: Varieties that flower only on growth produced the previous year.
Pruning should consist of cutting out weak or dead stems as soon as they are finished blooming in May or June. Pruning later than June or very severe pruning will result in fewer blooms the following spring.
Group B: (Group B is divided into two sub-groups.)
B1: Varieties that flower on wood that has been hardened by the previous season’s growth.
In late February or March a light pruning with some variation in the length of the stems will help produce a well balanced plant. Any weak or dead wood should be removed at this time, and a careful spacing of the remaining stems is all that is required. A severe pruning will reduce the number of blooms at the plant’s next flowering, but will not hurt the plant; in many cases it will help produce a better balanced plant.
B2: Varieties that flower simultaneously on last year’s growth and the current season’s growth.
For pruning purposes these varieties can be treated either as group B1 or group C. For that reason Group B2 varieties work extremely well in combination plantings with group B1 or group C varieties. If planted alone, a group C pruning regime every second year is recommended.
Group C: Varieties that flower only on the current year’s growth.
Plants should be cut back in late February or March to two strong sets of buds on each stem as close to ground level as possible. This will provide a plant with blooms that start near ground level and continue to the top of the plant.