Exotic passion flowers look as though they are tropical plants, but they can be grown almost anywhere, including much colder areas. You may even find these seemingly delicate vines growing along the side of the road. Some passion flower species are becoming invasive in warmer climates.
The genus Passiflora contains more than 500 species, so the common name passionflower can describe a number of different plant types. Some are shrubs, annuals, perennials, and even trees—some also produce edible fruits. They all share exotic flowers that remain open for only about one day. The flower has a wide, flat petal base with five or 10 petals in a flat or reflex circle. The ovary and stamens are held atop a tall, distinctive stalk that is encircled by delicate filaments. The stigmas start high above the anthers and slowly bend backward for easier pollination. Where they are hardy, passionflowers are usually trained on a trellis, fence, or other vertical structure. The flowers are extremely attractive to butterflies and other pollinators. In regions where they are not hardy, passion flower plants are often grown in pots and moved indoors to overwinter.
|Botanical Name||Passiflora spp.|
|Common Names||Passionflower, passion vine, maypop, granadilla|
|Plant Type||Most are perennial vines; some are annuals or woody shrubs/trees|
|Mature Size||Varies; some species grow to 30 feet|
|Sun Exposure||Full sun to partial shade|
|Soil Type||Rich and moist|
|Soil pH||6.1 to 7.5|
|Flower Color||Blue, purple, pink, white, and red|
|Hardiness Zones||5 to 11, USDA (depends on species)|
|Native Area||Mostly Central and South America; also North America, Southeast Asia, Oceania|
How to Grow Passion Flower Plants
Most species of passion flower should be grown in full sun to part shade, in average soil that is well drained. A sheltered locations, such as against a garden wall, is recommended for many species. If you bring potted specimens indoor for the winter, give them bright, indirect light and keep them out of drafts. Minimum indoor temperature is about 50 degrees. If you are bringing your passionflower indoors for the winter, it will probably go semi-dormant and look less than ideal, but it should perk up again in the spring.
To protect borderline plants during winter, stop feeding in late summer. Mulch the area around the roots, once the soil temperature drops, to prevent freezing and thawing throughout winter.
The more tropical the climate, the more pests there are to attack passionflower. Insects pests may include scale, spider mites, and whiteflies. Leaf spotting is generally caused by a fungal disease; remove affected leaves to slow the spread and treat with a fungicide if necessary. Root rot is common in soils that do not drain well.
Some species of passion flower spread so aggressively that they are considered invasive in some regions. Check with local authorities before planting passion flower, and make sure to supervise them to keep them from spreading uncontrollably.
To keep your passionflower vines healthy and blooming, plant them in full sun to partial shade. In extremely hot climates, some afternoon shade is appreciated. Passionflowers generally need at least four full hours of sunlight a day; more in cooler climates and some partial shade in the hottest areas.
The soil should be well-draining, but rich. Passionflowers grow and bloom best when the soil is kept moist. Soil pH can be in the neutral range, anywhere from about 6.1 to 7.5. The addition of compost to the planting hole will help provide nutrients, and mulch around the plant's base will assist in retaining moisture. Some type of support is needed for the vines to grow on—a trellis, a structure, or even another plant.
Passionflowers should be given a deep watering immediately after planting. Passionflowers thrive with one or two deep waterings per week throughout the growing season, providing about 1 to 1 1/2 inch of water every week if there is no rain. They do not handle drought well.
Temperature and Humidity
Passion flower plants may need winter protection in cooler regions. In zones cooler than zone 6, they often die in the winter unless you bring them indoors. Plant them in an area that's protected from wind, as strong wind can damage stems and burn leaves.
Passion flower vines are heavy feeders. They benefit from a regular, light application of lower-strength, balanced, general-purpose fertilizer with equal proportions of nitrogen, phosphorus, and potassium. Fertilize the plant before new growth emerges in early spring, and then repeat every four to six weeks until early autumn.
Passion flowers are low maintenance during the growing season and do not need to be deadheaded. Pruning is done to keep the size in check, to remove deadwood, and to make the plant fuller.
Some varieties will not require any pruning, but pruning does result in a fuller plant. Pruning can be done in late winter or early spring. In cooler climates, the vines may die back to the ground anyway. These plants flower on new growth, so make sure to prune them before growth begins in spring in order to preserve the season's blooms.
Growing in Containers
Many gardeners prefer to grow their passion flowers in containers. Passion flowers grow quite happily in a pot and offer you the convenience of being able to move them to a sunnier site or even bringing them indoors for the winter. Plus, growing in pots prevents passion flowers from spreading uncontrollably.
Use a potting soil rich in nutrients, and make sure the pot has good drainage. Keep the soil moist but don't allow the roots to soak in water. Plants grown in containers will need more regular feeding since they are watered more frequently, with nutrients rinsing out as the soil drains. If you are bringing the plant indoor for winter, but the stems down to 1 to 2 feet high before moving it.
Growing from Seed
Most varieties of passionflower can be purchased as seedling plants. They can also be propagated from either seed, softwood cuttings, layering, or rhizomes.
- To save seed, allow the fruits to ripen completely. Open the pods and remove, clean, and dry the seeds before storing. If you are saving seed from hybrid varieties, remember that they will not grow true from seed, but will revert to the appearance of the parent species.
- Passionflowers seeds can be slow to germinate. Start seed indoors by scarifying the seeds and soaking for 1 to 2 days in warm water. Discard floating seeds, as these are not viable.
- Place the well-soaked seeds on the surface of damp potting mix, pat down, but do not cover since they need light to germinate. Place the pot in a plastic bag and seal to retain moisture. If you can provide bottom heat (heat mat) to the pot, you will speed germination.
- It can take 10 to 20 days for passion flower seeds to sprout. Keep the soil moist at all times. When sprouts do appear, keep them out of direct sunlight until there are true leaves. Grow lights are best.
- Harden off the plant by slowly introducing it to outdoor conditions, extending the amount of sunlight it receives each day. Harden off the plant for 10 days to two weeks.
- Transplant once the plant gets large enough, possessing several sets of leaves.
- If direct sowing seeds outdoors, wait until danger of frost has passed and temperatures reach 55 degrees F.
Varieties of Passion Flowers
Common varieties include:
- Passiflora caerulea (blue passionflower): zones 7 to 9, grows to 25 feet with blue flowers
- Passiflora coccinea (red passionflower): zones 10 to 12, grows to 12 feet with red flowers
- Passiflora incarnata (purple passionflower): zone 5 to 9, grows to 8 feet with violet flowers
- Passiflora incarnata 'Alba': zone 5 to 9, grows to 8 feet with white flowers
- Passiflora alata 'Ruby Glow' (fragrant granadilla): a very fragrant variety with 4-inch flowers with cranberry petals and rich purple filaments.
- Passiflora edulis: usually grown for the edible fruit; grows to 5 feet.