In Colorado, planting clematis in the spring is generally more successful than fall planting. Vines do best in full sun and bloom poorly in more than a half-day of shade. A trellis or other support is helpful in windy periods.
Plant clematis in a soil that drains well and is amended with organic matter such as compost. The crown, the part of the plant where the stem and roots meet, should be about two inches below the soil. Keep plant roots moist and cool by using mulch. However, clematis roots do poorly when the soil around them is water-logged.
Supply four to six inches of an organic mulch (compost, wood chips) in the spring over the plant's root system.
Prune clematis to promote flowering. There are two different kinds of clematis and you need to determine which kind you have before you prune. Woody-stemmed types like the Montanas bloom early on last year's stems. Prune plants after flowering to remove deadwood.
Large-flowered Henryi and Elsa Spaeth hybrid types also should be pruned this way. Types that bloom on the current year's growth should be cut back in early spring to the first pair of healthy buds. These include Clematis x jackmanii and Clematis 'Ernest Markham' hybrids among others.
Well-established clematis will bloom for generations.
Adapted from: Colorado
State University Cooperative Extension
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See also Annual flowering vines and Clematis Pruning