What is Passion Flower?
The name passion flower (Passiflora spp.) is associated with an entire genus of plants. They are mainly vines. A few are trees or shrubs. Most are native to Mexico, and Central and South America though other members of the genus are found throughout the world. The plants are known both for their distinctive flowers and their fruit.
The passion in the name refers to the crucifixion of Jesus. The association was made by Spanish Christian missionaries. Different parts of the plant and flowers were assigned meanings to the story of the crucifixion. For instance, the most well-known is that the flowers’ radial filaments represent the crown of thorns that Jesus was forced to wear.
The passion fruit is the fruit of the passion flower. It is popular both for eating raw and for cooking. The size and flavor of the fruit depends on the species of passion flower that produced it.
How to Grow Passion Flowers
Most passion flowers are tropical plants. Outside of tropical areas they are grown in containers and brought indoors during the winter.
They will grow in full sun to partial shade. In tropical areas, it is best to plant them in a spot where they will get afternoon shade to protect them from scorching afternoon temperatures. They prefer rich, well-drained soil with a pH of 6.1 to 7.5. They also need to be watered regularly, 1 to 1 ½ inches per week.
Passion flowers are heavy feeders. Plan on fertilizing them every 4 to 6 weeks with a balanced fertilizer such as 10-10-10.
How to Grow Passion Flowers in a Container
Thankfully for us northern gardeners who love passion flowers, they grow well in containers so that we can bring them indoors during the winter. Use rich potting soil, water frequently (containers dry out quickly) and fertilize often using the same balanced 10-10-10 fertilizer. You will need to fertilize weekly because the constant watering needed to maintain your plant in its container also washes away nutrients in the soil very quickly.
Plan on bringing your plant indoors in the fall when night time temperatures fall below 50⁰F. You can overwinter it in one of two ways.
A lot of gardeners prefer to allow their plants to go dormant during the winter indoors because they require little care. Store your plant in a cool, dark place such as your basement. It will drop its leaves. This is normal. Water it about once a month. You want to keep the roots moist so that they don’t die. In the spring when night time temperatures are above 50⁰F, you can bring your plant back outdoors and it will start growing again.
As a Houseplant
Alternatively, you can bring your plant indoors and grow it like your houseplants. Since passion flowers need full sun outdoors, you will want to place your plant in the sunniest window in your home. A south-facing window is best. Water regularly to keep it moist as you did when it was outdoors. Our homes are too dry for these plants so you will need to provide humidity for them either by misting them regularly or by creating a humidity tray.
A humidity tray is a shallow pan that you fill with ornamental gravel (not the gravel form your driveway!) and then fill with water. Place your plant on top of the gravel. As the water evaporates, it creates a humid environment for your plant. Be sure to keep refilling the tray to provide constant evaporation.
You can bring your plant outdoors in the spring when night time temperatures are above 50⁰F.
How to Prune Passion Flowers
Passion flowers should be pruned in the early spring. They bloom on new wood which means that the flower buds are formed on the new growth in the current year. If you wait too long to prune, you will risk pruning away the developing buds and end up with few flowers or none at all. While you are pruning, be sure to also get rid of any dead branches.
Passion flowers that die to the ground in the fall do not require any pruning in the spring.
How to Grow Passion Flowers From Leaf Cuttings
You can propagate your passion flower from cuttings using leaves. Choose a healthy leaf on your vine. Carefully remove the leaf from the vine. Do not detach it from its stem. Do not detach the stem from the vine. Instead cut a small slice from the vine that includes the bud from which the leaf and stem grew.
Plant your cutting in a container deep enough so that only the leaf shows above the soil. Place the container in a sunny window and keep the soil moist. When new growth appears, you will know that your cutting has rooted.
How to Grow Passion Flower From Seed
Passion flower seeds can be started any time. They have hard seed coats, so you will need to soak the seeds 1 to 2 days to soften them. After soaking them, surface sow them in a container of pre-moistened soil. I have found that if I water after I sow my seeds, both the soil and the seeds wash away. Do not cover the seeds. They need light to germinate. Cover the container with a plastic bag to create a humid environment. You can also place your container on a heat mat to warm the soil and hasten germination.
- Light: Bright light, especially during the summer growing season. Full sun is preferable in the summer, with as much light as you can give during the winter.
- Water: Keep the plants moist at all times during the growing season, and you might have to water larger plants twice a day in heat. During winter, reduce watering but don’t let them dry out.
- Temperature: Warm in summer (household temperatures are fine) and colder in winter months (down to 50˚F at night). They are generally hardy, and even if they die back to the soil, they will likely recover next spring.
- Soil: A rich, fast-draining mix is ideal.
- Fertilizer: Fertilize adequately during the growing season, with controlled-release fertilizer and liquid fertilizer.
Passion flower is easy to propagate with leaf-tip cuttings. Take cuttings in the spring. Strip off a few leaves to expose nodes and bury the cutting in moist seedling starting soil.
Keep in warm and bright place until new growth emerges. Rooting hormone is likely not necessary as passion flower easily roots from cuttings.
Repot young plants every spring into a larger pot. Older plants can be stretched out every few years between repotting. To control their size, it’s best to cut your passion flower down in the fall, leaving only a few vines of between 15″ and 20″ long in the pot. Be aware, however, that plants trimmed in this way will still need to be repotted or at least refreshed.
There are several varieties of passion flower. In subtropical and tropical regions, these are used as butterfly and landscape plants, and collectors pride themselves on large collections. Indoors, however, by far the most commonly grown passion flower is the blue and purple Passiflora caerulea, which has a number of named hybrids. The P. incarnata also features blue flowers, with a more frilly appearance. Red passion flowers include the P. manicata. In general, the blue passion flowers are a bit more well behaved in comparison to the red flowering species, which can be monstrously aggressive growers.
Passion flower vines have deeply lobed leaves with flowers that hang or peek out from the leaves.
Some of the species have edible fruit, which is a sweet and delicious tropical fruit. As vines, they can pose a challenge to the indoor grower. Outside, passion flowers are grown on walls, fences, and trellises, where they are frequented by many varieties of butterflies. Indoors, however, their sprawling vines can be troublesome. One particularly effective way to manage their growth is to train the vines around a wire support, such as a loop of wires forming a giant oval above the pot. In terms of pests, the greatest danger is usually mites or mealybugs. Both can be controlled with insecticidal soap. Lastly, passion flowers are rampant growers during the growing season and benefit from plenty of sunshine, water, and fertilizer, as well as frequent pruning, which can even stimulate more blooms.