We have two in our garden, one a bog standard one, only cost a coule of quid. This has flowered since it was about 3 years old. The other was "Black Dragon" supposed to have scent & dark flowers, cost me in excess of �30! It flowered once after 10+ years, very poor only a couple of racemes, very pale, spindly & no scent. Pruning is definately the way to get them going. I don't know if it's an old wives tale, but they are said to "like their roots in the shade & shoots in the sun." Hope you succeed