I have anosmum (a nobile type) and don't water at all. The long canes get pretty shrivelled, but I don't yield. When they finally start popping out flower buds along the shrivelled canes and the new green growths start, then I water. They look like this as the buds emerge
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I still don't water until the buds get at least 1/2" long and the new green growths are emerging at the base. Then I resume full water/fertilizer, just like that. I tend to baby the canes to keep from breaking off any buds.