Flowering in spring, summer or fall, the dramatic flowers of climbing clematis (Clematis spp.) add flair and charm to any landscape. While the dense, scrambling vines look lovely covering a fence during the growing season, winter brings a brown and scraggly plant, making pruning an inviting chore. Clematis vines vary in their pruning needs depending on their flowering category, so knowing which group your clematis belongs to is helpful in knowing the proper time to prune out old vines.
Named for the Greek word for “vine,” flowering clematis is beloved for its wide variety of flower colors, growth habits and broad hardiness range. Depending on the hybrid or cultivar, clematis is hardy from U.S. Department of Agriculture hardiness zones 3 through zone 7 or 8, and so can be grown across a broad portion of the United States. Hybrids are available in virtually any color and two-color combination, with flowers that range in size from petite, 1-inch blooms to knockout blossoms more than 3 inches across. They are picky about light and soil: Plants look best with at least six hours of direct sunlight each day and some afternoon shade and prefer to grow in moist, well-mulched soil away from competition by other roots.
Individual clematis cultivars or hybrids are classified into one of three groups depending on their bloom times: Group A, or early-flowering; Group B, or summer-flowering hybrids; and Group C, or late-flowering. Early-flowering types bloom in April and May in most areas, and only from last year’s buds. Most summer-flowering hybrids produce two flushes of blooms, once in early summer on last year’s growth and a second, smaller show in late summer on new wood. Late-flowering types flower on the current season’s growth, and though most plants in this category flower from late summer onward, some types can begin in June along with the summer-flowering group.
When to Prune
Group A clematis are the most challenging to maintain, as they always require some old wood to flower properly. They should always be pruned immediately after flowering has finished, but not later than July, to allow the plant to produce buds for the following season. Plants falling into Group B and C are both best pruned in late winter or early spring, from February to March, and differ mainly in the severity of pruning. Clematis does not necessarily require any pruning at all, but plants left to their own devices will be rangy, and flowers will tend to cluster only near the ends of the vines.
When pruning any type of clematis, the goal is always to remove dead and weak material, restrain the plant to a particular area and encourage dense, well-distributed flowers. For Group A plants, wait until after flowering has concluded, then cut all vines back, including those that just finished blooming, to the first pair of healthy leaf buds on each vine. For Group B plants, wait until late spring when leaf buds begin to swell on the vine, and cut each vine back several inches to a foot to the first pair of large, healthy-looking buds. Re-pruning after flowering may encourage a second flush of bloom. Group C plants flower on the last few feet of each vine, and should be cut back to 2 or 3 feet in early spring, removing old, brown vines as well as some healthy shoots.
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