Passion flowers, passion vines and maypops are all names for the exotic passion flower. Most passion flowers are vines, although you can find hybrids that take shrub and, very rarely, tree forms. Passion flowers take well to container life and can be grown outdoors in sunny south-facing gardens or indoors as tropical houseplants during the winter.
Passion flowers need to be planted where they will receive at least four hours of full sun a day as well as some afternoon shade. Passion flowers can be planted in any well-draining soil with a neutral pH (6.1 to 7.5). Dig a hole slightly larger than the root ball. Add a handful of compost to the bottom of the hole before planting to make this heavy feeder happy. With a height between 4.5 to 9 metres (15 to 30 feet), passion flower vines need some sort of support. Plant your passion flower along a wall or fence or next to a trellis. Passion flower vines use tendrils to attach themselves to their support, so no tying is needed. Passion flowers need to be kept evenly moist and the roots need to stay cool. Their shallow root system can make this a challenge. Using organic mulch -- straw, shredded bark or leaves -- 5 to 7.5 cm (2 to 3 inches) deep around the base of the plant works to cool the roots during the summer and hold moisture. In spring, use a commercial 10-5-20 liquid fertiliser every six weeks until late summer.
Passion flowers flourish in containers as long as they have a trellis or other support. You can use any general potting soil for passion flowers, but the container needs to be deep enough that it won't tip over when the passion flower reaches its full height. Fertilise as you would passion flowers planted in the garden, remembering to stop fertilising in late summer. In the autumn before the first frost date, move your plant indoors placing it where it will receive bright, indirect light. Keep your plant evenly moist but do not let the soil get soggy. Use a water catcher under the pot and discard the collected water. Your passion flower can go back outside in spring after all threat of frost has passed. Before setting your passion flower outside remove it from the container and replace half the soil in the pot with new potting soil. Mix the remaining soil in the container with the new potting soil and re-pot your passion flower. You must replace at least half the soil as the passion flower's heavy feeding, even with added fertilising, removes nutrients from the soil faster than additional fertiliser can add them.
Passion flowers make exotic houseplants and can live for years with proper care. Use a general purpose potting soil in a container three to four times larger than the root ball. Fertilise as you would passion flowers planted in containers and in the garden. Place your plant where it will receive bright, indirect sunlight but will be out of draughts. Keep the room your passion flower is in above 10 degrees C (50F). Keep the soil evenly moist and mist the plant once or twice a month. In winter allow the soil to dry out slightly before watering. To keep your passion flower at a suitable height, prune the growing tips off the vines at the height you want your passion flower to remain.
Prune passion flowers in spring just after it starts growing. Make your cuts just above a node (the spot where leaves emerge) as new growth will emerge from the node. Remove all dead wood and pinch back side shoots for a bushier plant. To keep your passion flower at the height you want it, you can cut back the top at any time during the growing season. In autumn, cut container plants back to 60 to 120 cm (2 to 4 feet) tall to make moving easier. Remove the dead vegetation before settling the plant in for the winter.
Passion flowers do not grow well from seeds. It can take months before germination and the babies will not look like the parent plant and will have different characteristics like winter hardiness and flower colour. To start a passion flower from seed, clean the seed thoroughly and allow it to dry. Using a fine grit sand paper lightly score the outside of the seed coat. Place the seeds in a container of water and leave them for one to two days. Viable seeds will sink to the bottom; discard floating seeds. Use a sterile seed starting mix placing the seeds 6.5 to 13 mm (1/4 to 1/2 inch) deep. Place the potted seeds on a seed warming mat, on top of a refrigerator or anyplace where the soil temperature will be about 21 degrees C (70F). Place the seeds in a bright spot out of direct sunlight. Keep them evenly moist.
You will need to keep the flower crown from freezing during winter. Your passion flower will die back to the crown after the first frost. Remove the dead vegetation and any mulch. Pile straw loosely to a depth of 7.5 to 12.5 cm (3 to 5 inches) over and around the crown. Remove the straw in spring after all danger of frost has passed. If you are growing passion flowers in containers simply move the container indoors. Place the container in a room that receives bright, indirect light and stays above 10 degrees C (50F). If you are using a garage or other outbuilding to overwinter your passion flower, wrap burlap around the plant to protect it from the chill.