Passionflower vines, or Passiflora incarnata as the genus of plants is known botanically, are fast-growing fruiting and flowering tropical vines. They are desired as garden plants for their rapid establishment habit, intricate exotic flowers, sweet tart fruits called maypops and their few care requirements. Passionflower vines are hardy in USDA zones 6 through 9, flowering throughout the summer and fall in warmer climes, with fruit development following bloom.
Select a planting location with full sun exposure, protected from winds and near to or with a support structure for the vines to spread over and out in the sun. Arbors, sturdy fences, loggias and heavy-duty wall trellising are ideal options, as you want to support the weight of the plant, flowers and fruit at peak production.
Provide a well-drained and nutrient-rich soil. If soil is heavy and slow-draining, amend with several pounds of sharp sand to speed water flow through the soil. Boost the soil nutrition by amending it with several pounds each of quality compost and well-aged manure tilled into the top foot of soil. Nutrient-rich soil means you can refrain from chemical fertilizers.
Water your passionflower vine regularly throughout the growing season to keep the soil evenly moist but not soaking wet. In dry climates or during the peak of summer growth, this may translate into watering every other day to once per week or less in spring or winter. Never allow the soil to dry out entirely, and always water when the soil feels dry to the touch an inch down.
Harvest ripe maypops in the summer when the skin of the fruit deepens in color and becomes just slightly wrinkled. Maypops will also fall to the ground when ripe, so pick them up immediately to eat or process for canning or frozen storage. Allow maypops to ripen on the vine, as they do not sweeten significantly once plucked.
Prune your passionflower vine when needed to control the shape and size or climbing position. Always prune in the spring well after the last threat of frost has passed and remove only up to one-third of the plant mass in each pruning session. Reconnect or weave the vines back onto the support when cuts are made to mature woody vines to maintain stability of the plant.