Why won’t my passion flower bloom?

Isabel in Clinton, Ontario, asks:

I have a passion flower plant that’s growing green leaves but not many flowers. Last year it grew in a tight mass of leaves and plenty of flowers, but they were mostly on the inside so they were hard to see. This year I made it a trellis so it could grow freely and that it has, but there have not been many flowers to enjoy.

I water it and fertilize it daily. It has lots of new growth and wonder if trimming it back might be the answer. It’s beginning to grow up on the awning and that is at least six feet (1.8 m) high.

Judith Adam, horticultural consultant for Garden Making, replies:

You might be providing too much good care for your passionflower vine (Passiflora spp.). Daily fertilizing, even at a low rate, is probably an overdose of encouragement. The lengthy vines may be due to too much nitrogen. Switching to another fertilizer with a high middle number (such as 5-15-5 or similar analysis) and feeding every three weeks, may prompt more flowers. The middle number in fertilizer analysis is phosphorus, which stimulates root growth and flower bud set.

Cut the vine back by half its length and see if it will use the new fertilizer to bloom as expected. Take the plant indoors before frost occurs.

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