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Gardening | Is pruning or deadheading best for clematis?

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Recently a reader asked me whether to deadhead clematis or not. The question seems simple enough – yes or no. Surprisingly, though, the answer is not so straightforward.

Clematis bloom whether you prune them or not. Deadheading – removing dead flowers – makes some plants more floriferous, but only those that are fertile. A number of clematis hybrids are sterile, which means that deadheading has no effect on their production of blooms.

Another question to ask about clematis is whether to prune or not. Again, the vines bloom whether you prune them or not. However, the vines are tidier with more prolific blooms when they are properly pruned.

The plant tag that comes with a clematis indicates if the plant is in pruning group 1, 2 or 3, sometimes called A, B or C. The number or letter indicates how and when the plant should be pruned.

If you know your clematis variety, you can readily find its pruning group online by typing the plant’s name (common or botanical) plus the words “pruning group.” If you don’t know your clematis name or pruning group number, you can easily determine what it is by watching when your plant blooms. Does it bloom spring and fall, with a large flush of blooms in the spring followed by sporadic blooms throughout the season, or only in summer or fall? You will also need to note if it blooms on last year’s woody growth or this year’s green flexible stems.

The trick to understanding your clematis is to know when it blooms and whether it blooms on new growth or old wood.

The first year after planting, all groups are pruned the same way. Late winter-early spring, cut each stem back to 5 inches from the ground. You won’t get blooms the first year, but it is worth sacrificing them for the plant’s future growth. It will produce a stronger, bushier plant in future years.

Group 1 clematis are early season bloomers. They flower with a strong flush of blooms in April and May. These clematis do not necessarily need pruning. When the plant becomes tangled and unruly, stems can be trimmed from the top and sides of the plant. Do not cut the woody main stems. Typically, these plants do not die back in the winter; they are evergreen or semi-evergreen. The plants bloom on old wood, so wait until just after flowers fade, and then prune. Give Group 1 plants time to develop the new growth that will produce next year’s flowers.

Group 2 clematis produce mid-season blooms in May – August on the previous year’s woody growth. Prune lightly after spring flowers have faded. This is the time to get rid of broken and dead wood and tangled areas, and trim the plant into shape. This group blooms again, although less vigorously, in late summer on new green growth. Group 2 includes the large, flowered, showy hybrids and cultivars. Familiar varieties include Belle of Woking, Nelly Moser and Henryi.

Group 3 produces late-season blooms on the end of new growth in late summer or early fall. Members of this group are vigorous growers and should be cut back to 12 inches from the ground in early spring. Sweet Autumn Clematis, Comptesse de Bouchaud and jackmanii are well-known group 3 members.

Each group of clematis has a specific bloom time. Neither deadheading nor pruning affects that. Heavy pruning is useful when a vine becomes too heavy for its support structure or when it becomes unkempt and straggly. Be aware that heavy pruning, in some instances, can delay bloom time a bit, and severe pruning on groups 1 and 2 can prevent blooming for a year.

Clematis are low-maintenance plants. Prune your plants at the right time just once a year to stimulate growth and blooms.

Reach DEBBIE MENCHEK, a Clemson Master Gardener, at dmgha3@aol.com.

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