The Clematis is a genus from the buttercup family (Ranunculaceae). They are native to temperate zones and to the mountains in the tropics. The species from the temperate zones are deciduous and those from the warmer areas are evergreen.
The word clematis is derived from the ancient Greek word klema and means ‘climbing’. The leaf stems wind themselves around stems, branches or other materials to hold on and climb up.
The Clematis prefers rich, cool, well-drained soil with enough moist and in a sunny spot. When planting a new deciduous Clematis it is best to plant it about 10 centimetres (4 inches) deeper than the rim of the pot. The evergreen Clematis are best planted at the same height as in the pot. It is best if you cut every new Clematis, regardless of which group, back to about 15 centimetres (6 inches) from the ground in March. This will stimulate a stronger and bushier growth.
The large-flowered Clematises are more susceptible to clematis wilt than the small-flowered ones. This disease can be recognized by a sudden collapse of the stems and flowers. The clematis wilt is caused by a fungus and the most common cause is a soil that is too dry.
There are three pruning groups based on flowering time:
Group 1: Bloom before half May. This group flowers on shoots that where produced in the previous summer (old wood). It is best to prune this group right after flowering. Remove all dead and damaged stems. You may cut away some of the old branches or shorten branches that have grown too long, but do not cut away too much. Examples of Clematises from this group are Clematis montana, C. macropetala, C. alpina and C. armandii.
Group 2: Bloom before end of June and large-flowered. This group also blooms old wood, but often blooms a second time in late summer on new shoots. In March you remove dead and damaged stems and cut back the remaining stems to a pair of robust buds. If you prune to heavy it will reduce the amount of flowers in spring. After the spring bloom you can prune harder. You cut back stems to a healthy side shoot or strong set of buds just below the spent flowers. This will stimulate new growth and a second flush of flowers. Examples of Clematises from this group are Clematis ‘Guernsey Cream’, C. ’Nelly Moser’ and C. ‘The President’.
Group 3: Starts to bloom from July. This group blooms on new wood that has grown in the same year. You can cut back the stems to 15 – 30 centimetres (6 – 12 inches) from the ground. Do not prune later than March because then the stems may blood and the Clematis may not survive that. Examples of Clematises from this group are Clematis fargesii, C. jackmanii, C. diversifolia, C. viticella and C. flammula. Deadheading spent flowers will prolong the flowering time.
The Clematis ‘Guernsey Cream’ blooms in May/June on old wood and also on new shoots in August. After bloom decorative seed heads develop. The flowers are light green in the beginning and then turn milky white. The flowers are larger in spring than with the second bloom.
Attracts bees: yes
Exposure: sun/ part shade
Flower colour: white
Flowering time: May - August
Foliage colour: green
Fragrant flower: no
Hardiness: -30 ºC (-22 ºF)
Height: 10 feet (3 m)