Answer: If it bloomed once but not since, the growing conditions are not quite right. A possibility is that the spring frosts have damaged the buds year after year.This plant blooms on old wood, meaning the growth made the previous year. So excessive pruning in summer, fall, winter, or in the spring before bloom time would decrease or eliminate the flowers. The best time to prune is in spring right after the plant blooms (or would have bloomed) at which point it should be cut back very hard. As the season progresses a bit of tip pruning can be done to try to control and direct the growth, but drastic pruning should be avoided. Finally, excess shade will reduce blooming (the plant prefers full sun) and excess nitrogen fertilizer will reduce blooming and cause excess vine growth. Some authorities suggest root pruning, meaning slicing downward with a sharp spade close to the vine on one side to sever half of the roots and thus shock the plant into feeling threatened and stress it into blooming in an effort to produce seed and reproduce itself -- but I have not personally seen this succeed. Maybe, with a little luck, this will be year the vines finally bloom for you! Otherwise, there isn't a whole lot you can do, then and again patience is said to be a virtue.
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