Answer: In my experience this vine will naturally become somewhat bare at the base as it matures because the foliage tends to cluster at the tips. To counter that, you could selectively prune some of the longest vines back to the ground or back to about two feet to try to encourage new growth from the base while still maintaining the height. This will not hurt the vine if you do it in late winter or early spring since it blooms on new wood, in fact it may stimulate additional blooming and will also help you keep the plant under control over time. Do not prune the vine in summer however or you will be removing flower buds.
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