I have followed all the advice found on getting my vine to flower again, to no avail They thrive in rainy Dublin, growing among hedges and up hydro poles but not in Toronto. Ed Lawrence suggested the addition of coffee grounds for more soil acidity, ensure lots of water, shade the roots in the p.m. and less N fertilizer. Nothing. There is going to be a trick which, I will continue to search for and will let you know.
The Passiflora caerulea (Blue Passion Flower) is a vigorous growth, large, semi-evergreen, perennial vine that climbs with twining tendrils. This vine loves the heat of a stone or brick wall at its back, or even a hydro pole!
Passiflora will flower in alkaline, as opposed to a nitrogen-high growing medium — hence the advice to not apply only ‘N’ fertilizer. A fertilizer that has double the phosphorous than nitrogen, say 10-5-20 would promote both good vine growth, as well as robust flowering — rather than only lush, green foliage. Your local nursery should help with the right brand selection, and make every effort to follow the application instructions to the ‘T’.
And if “rainy Dublin” is your experience with Passiflora, then yes, in fact, watering should be deep, that is, long drinks at a time, to soak downwards, a direct invitation to the roots to also travel downward. The result: the plant will develop a root system able to survive frost, and drought. The Passion flower’s root structure is very similar to a grape vine’s.
Re flowering: you mention: ‘getting my vine to flower again”. In addition to this fertilizing and watering advice, remember that Passiflora produces flowers on new spring growth, so your plant should be pruned in late winter/ very early spring, but no later.
Finally, you might want to also read HERE a prior answer to another gardener’s question, that is relevant to yours.
And please do let Toronto Master Gardeners know of your future results!