glenon I have lots of passion flowers on my fences and I never trim them back.
They are growing just fine! Did not notice a decline in fritelary butterfly
caterpillars. But interesting enough, they usually stayed on the wild
passion flowers that grow naturally here.

--
gloria - only the iguanas know for sure

i agree with glenon i would just leave your vine unless its in real need of pruning back.
heres a link that might help u some.

http://www.supermarketguru.com/page.cfm/1393
good luck, sockiecat.