Answer: The roots have stored energy which is replaced by photosynthesis (when sunlight is absorbed by the leaves) so cutting back the new growth as soon as it emerges will eventually deplete the stored energy and kill out the roots. You can help things along by immediately brushing the stumps of the leaves after you've pruned them off with an herbicide such as Round-Up. This is a vegetation killer so be careful not to get it on any desireable plants or they will be killed, as well. Best wishes with your garden!
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