Taxonomy and origin
Passionflower is the common name for Passiflora, a genus of more than 500 species, or approximately 530, nearly all of them vines that climb by tendrils. It holds on with axillary tendrils, thin coils that grow at the leaf joints and wrap wire, string, or a neighboring stem, so it wants the same sort of thin support a clematis does. Five petals and five sepals open almost flat, and above them stands the corona, a crown of numerous fringelike segments. Out of the center rises a stalk bearing a ring of five stamens, and above those sit the ovary and three widely spreading styles. On maypop the flowers measure 4 to 7.5 cm across, and the leaves are alternate, palmate, three-lobed, and 6 to 15 cm long and wide.
Four species account for most of what American gardeners actually grow. Maypop, Passiflora incarnata, is native to the southeastern and south-central United States and to Bermuda. Blue passionflower, P. caerulea, comes from South America and is the national flower of Paraguay, with its native range listed as Brazil and Argentina. Purple passion fruit, P. edulis, the vine behind the fruit sold in grocery stores, is native to Paraguay, Brazil, and Argentina. Yellow passionflower, P. lutea, grows across a wide part of the south-central and southeastern states, a smaller plant with greenish yellow flowers and purple fruits. The four differ enough in cold tolerance, size, and fruit that most of the confusion around this plant comes from treating them as one.
The names record what people saw in the plant. The genus name joins the Latin words passio, meaning passion, and flos, meaning flower. The species name of the maypop, incarnata, is Latin for flesh-colored, though what it refers to is obscure. Maypop itself is older and blunter: stepping on a mature berry often makes a loud popping sound, which is where the name comes from. The plant fed people long before anyone planted it for its flowers, and Native Americans ate the young shoots and leaves cooked with other greens.
Bloom time
Passionflower blooms through the heat of summer and into fall. Published bloom windows for maypop run June to September and July to September; yellow passionflower opens its inch-wide flowers over the same June to September stretch, and the hardy hybrid 'Incense' concentrates its bloom in July and August. Each flower gets a single day. A maypop bloom opens and closes within that day, and passion fruit flowers do the same. What covers a vine in August is a rolling succession of one-day flowers, so the blooms you count one morning are a different set the next. Fruit follows on the same calendar. Maypops appear from July to October and ripen to a yellowish color with brown seeds by fall, and in Florida passion fruit ripens about 80 days after flowering, from late May to July.
Why your vine will not flower or fruit
A vine with no flowers and a vine that flowers heavily but sets no fruit are two different problems with two different answers. No bloom at all usually means the plant is too young, too well fed, or too shaded. Young vines do not flower until they reach maturity, which can take up to a year. Feeding is the next suspect: heavy nitrogen pushes a passion fruit vine into leaf and stem growth at the expense of flowers, too much manure or compost does the same to blue passionflower and gives lush growth with poor bloom, and the fix is to cut fertilizer rates back once the vine has reached maturity. These vines perform best in full sun and only tolerate some shade, so a plant that has climbed into a tree canopy or sits against a north wall is working with too little light. Water counts at the bud stage as well, since buds drop if the soil dries out far enough for the plant to wilt.
Heavy bloom with no fruit is almost always a pollination problem. The anthers sit below the stigmas, so the flower cannot easily pollinate itself and depends on insects or on a person with a brush. Wind does not fill in, because the pollen grains are heavy and sticky. Honey bees and carpenter bees are the primary pollinators of passion fruit, and the large bodies of carpenter bees carry pollen from stamen to stigma better than anything else at the flower. Maypop puts a second obstacle in the way. In a controlled trial, 122 flowers on five maypop plants collected from different locations were pollinated with their own pollen, and not one of them produced a fruit. Hand crosses between plants of different origins did work, at rates as high as 85 percent for one pairing and as low as 40 percent for another. In a garden that means a lone maypop, or a row of plants all divided from the same one, can flower for years and never fruit.
With passion fruit the answer depends on which form you planted. Purple passion fruit varieties and their hybrids are self-compatible and need no cross-pollination, while yellow passion fruit is largely self-incompatible and needs a partner for seed and fruit set; some varieties and hybrids fall between the two with partial self-incompatibility and should be planted alongside other varieties. Age is worth ruling out before you change anything, since a passionflower generally will not fruit until at least its second year. When fruit does form and comes up hollow or dry, look at feeding and water. Excess fertilizer can leave you with empty fruit, and a shortage of water or nutrients can leave the fruit without the pulpy arils that surround the seeds.
Finding the cause on your own vine
The two failures need different answers, so the checks separate them before anything gets changed. Stop at the one that fits the vine in front of you.
Which passionflower fruit is edible
Four fruits turn up on American vines, and they separate by size, color and where the plant came from. Identify yours before anyone eats it.
Winter, dieback, and what comes back
Winter takes the top of a hardy passionflower and leaves the roots alive. Maypop is woody where winters stay warm and dies to the ground where they turn cold, and blue passionflower shifts the same way by climate: evergreen in warm-winter areas, deciduous in temperate ones. The roots are the part that matters. Blue passionflower has come back from deep roots after temperatures of 5 degrees Fahrenheit with the ground frozen more than two feet deep, which is why a vine that looks like a bundle of dry string in March is often untouched below the soil line. The mistake gardeners make is reading dieback as death, digging the crown out in early spring, and planting something else on top of it.
These vines also come up late. Maypop emerges fairly late in spring, well behind the perennials around it, so mark the spot in fall and leave the ground alone until early summer before you judge the plant. In poorly drained wet soil the roots can rot. Mulch over the root zone, and in colder areas protect what stems remain by wrapping them with insulating fleece. One caution before you clear away the dead growth: the Gulf fritillary pupa is mottled brown and looks like a dead leaf, so in a garden that fed caterpillars in late summer, check what is hanging on those stems before it goes in the bin.
Tender species get no such second chance. Several of the ornamental passionflowers need a minimum temperature of 41 to 45 degrees Fahrenheit, and passion fruit and giant granadilla want winter temperatures no lower than 50 to 61 degrees. Below those thresholds the whole plant is lost, roots included. Purple passion fruit is winter hardy only in zones 10 to 12, which leaves most of the country growing it in a container that spends the cold months indoors at a bright window. That changes the shape of the growing year: the plant is cut back, carried in before the first cold nights, held through winter with less water, and restarted outdoors in spring, and a vine handled that way rarely reaches the size it would make in the ground.
Winter by zone, species by species
The same plant behaves differently across the country. Each band below carries what the top and the roots do, and the temperatures that go with them.
Pruning and cutting back
Prune passionflower once a year in early spring, and take out the old flowered stems. Cutting lightly at the end of summer, once the plant has finished flowering, also works, and the two timings sit together better than they look, because passifloras flower on new growth and can be pruned early in the growing season without costing the bloom. Spring work sets the size and framework the vine will grow from for the whole season, while the late-summer trim only tidies a plant that has already flowered. On a vine that dies back over winter, spring pruning stops being a decision at all and becomes the job of clearing dead stems off the trellis.
How hard to cut depends on what the vine has become. For routine work, cut flowered shoots back to two buds from the previous year's framework of stems. For a plant that has turned into a bare tangle up top with nothing at the base, renovation means cutting the stems back to 1 to 2 feet from the base, and that is a job for every few years at most, because it weakens the plant. Pruning too hard, too often does the same damage. The reason sits below ground: taking off too much top growth at once can weaken the roots and leave them open to fungal infection. Taking a renovation in stages, across successive springs, costs some size and saves the plant the shock.
In season the work is small and constant. Clip the shoots that have left the trellis and are heading for a gutter, a shrub, or a doorway, and tie in the ones you want, since tendrils grab whatever is nearest and it is rarely the support you built. A first-year plant needs none of this beyond guiding the shoots onto their support, because there is no framework yet to cut back to. Thinning has a second purpose beyond shape, since blue passionflower can develop fungal disease when air does not move through the growth. Clean the blades between plants and between jobs, because passion fruit woodiness virus travels on pruning tools and through grafting.
Pruning calendar
One job to a window, with the limit that goes with it.
Spreading, suckers, and the invasive question
Maypop spreads underground, and for gardeners who have had one for a few years that is the usual complaint. The plant develops a very deep perennial rootstock, and sprouts emerge from it, which is how a vine planted beside a mailbox ends up sending shoots through a bed on the other side of the walk. Control means going around and removing the root suckers on a schedule. Mowing handles the shoots that come up in turf, since they are cut with the grass and give up. A physical barrier, a raised bed, or a large container keeps the roots inside a boundary you chose. Digging out the parent plant seldom finishes the job, because that rootstock sits deeper than a spade reaches, so plan on a season or two of pulling shoots after you remove a vine you no longer want.
Whether it counts as invasive depends on where you garden and which species you planted. Purple passionflower may become invasive in some regions or habitats and displace desirable vegetation, and it appears on invasive listings compiled by several authorities. In Florida, where the plant is native, the same vine is treated as a possible nuisance if it grows out of control, and its tropical look and speed lead some gardeners to assume it is an introduced weed when it is not. The imported passion fruit is the clearer case: it is predicted to be invasive and is not recommended for Florida gardens. If you want the flower without the running roots, yellow passionflower is much better behaved in the garden than maypop.
Passionflower types worth telling apart
Hardiness is what separates these plants in practice, and flower color follows the species. Blue passionflower is the one that turns up on every list of blue flowers, and it is not the hardiest of the group.
Light
Passionflower flowers best in full sun, counted as six or more hours of direct light a day, and it will still grow in partial shade. For the native maypop the working floor is direct sunlight for at least half of the day. Below that the vine keeps climbing and the bloom thins out, because a shaded passionflower spends what it has on reaching light. Where the roots sit matters less than where the top ends up: a crown in the shade of a fence, with the growth running over the top into open sun, still flowers, which is how these vines live in the wild, hauling themselves out of brush and into daylight. That changes how you judge a site: read the light at the height where the vine will flower, over the top of the arbor or on the far side of the fence, before you judge the planting hole.
Water and feeding
Water passionflower about once a week during a dry spell, and water a container as soon as the surface of the soil looks dry. In open ground the pattern that suits it is a light hand with fertilizer and deep, infrequent soaking, which matches a plant whose roots run far enough down to survive a frozen winter. Containers reverse the feeding half of that, because every watering carries nutrients out of the drainage holes: a liquid feed every four to six weeks through the growing season keeps a potted vine in leaf and bud. Taper that feeding as the nights cool so the growth hardens with the season, and keep watering steady through late summer, when a fruiting vine is carrying flowers and fruit at the same time.
Cold hardiness and why the ratings disagree
Cold hardiness depends on the species. NC State lists Passiflora incarnata for zones 5a through 9b, while UF/IFAS rates passion flower for zones 7B through 11. The gap comes from what each rating is measuring. At the cold end the top growth is killed every winter and the plant is judged on whether the roots push new shoots in early summer, while a rating built around a vine that keeps its woody framework through winter starts much further south. Both are true descriptions of the same species in different climates. For a gardener the reading is practical: in the cold half of that range, treat passionflower as a perennial that behaves like a herbaceous plant, plant it where drainage is good and snow settles, and mulch the crown. In the warm half, expect a woody vine that holds its structure, keeps its leaves in mild winters, and needs pruning to stay inside the space you gave it.
Height, spread, and what it climbs
As garden climbers passionflowers are usually at least 10 feet tall, and the vines themselves run 2 to 6 meters long. Given nothing to climb, the same plant sprawls, with stems reaching about 6.5 feet across open ground, which is how it grows in pasture and along roadsides. Support decides the shape. Tendrils need something thin to catch: wire, netting, string, or the crosspieces of a trellis. A tendril climber will not wind itself around a bare post the way a honeysuckle does, so a smooth column, a wide rail, or a flat masonry wall gives it nothing to hold and the growth ends up back on the ground. Put the support in at planting, size it for the finished vine, and tie the first shoots in by hand until the tendrils take over the job.
Growing passionflower in a pot
A container is the standard answer north of the tender species' range, and the pot can be modest at the start: a young plant goes into one about 12 inches wide. Repot every two or three years, moving up a size and refreshing the mix, because a vine that has filled its pot with root dries out faster than anyone remembers to water it. Purple passion fruit will live indoors year round in a sunny room, flowering under glass where it would freeze outside. Choose depth over width, since the roots go down, and set the trellis or obelisk in place at planting so the tendrils have something to hold before the growth outruns you. A pot also solves the other problem this plant creates, since roots that would otherwise run through the bed stay where you can see them.
Pests and diseases
The insect most likely to strip a passionflower is the one the plant exists to feed. Gulf fritillary females lay small yellow eggs singly on the leaves, stems and tendrils, and the larvae feed on all parts of the plant and can defoliate a host vine quickly. The plant is not passive about it: some species carry pigmented callosities on the leaves that resemble butterfly eggs, which discourages females from laying there. The fritillary caterpillar eats passion fruit foliage and nothing else, and hand removal is the recommended answer where you want the leaves kept. A vine stripped in August is the host plant doing its work, not a plant with a disease. Beyond the caterpillars the native maypop carries no serious insect or disease problems, though it is susceptible to nematodes, which work below the soil line where nothing shows until the plant slows.
Real disease trouble concentrates on the passion fruit crop and on plants grown under cover. Fusarium wilt, caused by the fungus Fusarium oxysporum, shows as pale-green leaves, mild dieback, leaf drop on the lower leaves and general wilting on young plants. Passion fruit woodiness virus leaves foliage distorted and crinkled, patterned dark green with light-yellow spots, and aphids are the nuisance to watch on young growth. Root and crown rot comes out of wet soil, caused by Phytophthora, while anthracnose on fruit and stems comes from Colletotrichum gloeosporioides. Indoors and under glass the pest list changes to red spider mite, whitefly, scale insects and mealybug, which is the trade a gardener makes for keeping a tender vine through winter.
What actually goes wrong, ranked
This ordering comes from a sample of thirty-four threads and posts on garden forums and extension question boards, counted by how often each complaint appeared.
Five threads. Bare stems standing into late spring with nothing green at the base, and owners asking whether to dig it out or give it another month.
Five threads. Heavy bloom right through the season with every flower dropping and nothing swelling behind it, on vines the owners describe as otherwise healthy.
Five threads. Shoots reported several feet from the plant, coming up through other beds and through lawn, and one owner describing a fence line taken over in a season.
Four threads. Pot size, when to bring the plant indoors, and how much light it needs to get through the winter.
Three threads. Leaves yellowing and dropping while the plant loses ground, which puts wet soil and the root rot that follows it at the top of the list.
Two threads. Long stems and big leaves on a plant that is clearly growing hard, with no buds anywhere on it.
Two threads. Every leaf gone within days on a vine that looked untouched the week before.
Toxicity and pet safety
The poison listing on passionflower covers the leaves and stems, and names cyanogenic glycosides as the toxic principle. Poison severity for the native maypop is rated medium, and the symptoms recorded are severe nausea, vomiting, drowsiness and episodes of irregular heartbeat. The same entry flags the plant as a problem for cats, dogs, horses and children, which is reason enough to train a vine up out of reach of a dog that chews, or to fence the base of one growing where a horse can lean over it. Ripe fruit sits outside that listing, which is why the fruit of several species is eaten while the foliage is left alone. Eating the leaves as herbal medicine is not recommended, a caution worth knowing because the same plant is sold dried and packaged for tea.
The tea and supplement question
The supplement and the tea sold as passionflower come from this climbing vine, which has traditionally been used as a sedative. It is promoted today for anxiety, sleep problems, stress, attention-deficit hyperactivity disorder and pain. The National Center for Complementary and Integrative Health states that its effect on anxiety and other conditions has not been studied extensively, with a small amount of research suggesting that oral passionflower may reduce anxiety before a surgical or dental procedure. Possible side effects listed are drowsiness, dizziness and confusion. It may interact with some anesthesia drugs, so its use is to be avoided before surgery, and it is advised against during pregnancy because it may induce uterine contractions. People also boil the flowers and leaves to make a tea at home. Past that point the question belongs with a clinician who knows what else you take.
Meaning and symbolism
The name records what missionaries read into the flower. Roman Catholic priests in Latin America used parts of the flower to symbolize the Passion of Christ, and early Spanish explorers described its appearance as representing the sufferings of Christ. In that reading the corona is the crown of thorns, the styles are the nails, the stamens are the wounds, and the sepals and petals stand for the apostles: five of each, ten in all, with Judas and Peter left out of the count. The reading traveled with the plant and stuck to the whole genus, which is why a wild vine on an Alabama fence row carries a devotional name. Closer to home the same species is Tennessee's state wildflower, and its lavender coloring puts it among the purple flowers gardeners plant for that end of the range.
Myths worth clearing up
Four beliefs follow this plant around, and each one changes what a gardener does with the vine.
The myth: Every part of a passionflower is poisonous, fruit included.
The reality: Ripe pulp is eaten from several species. Maypop pulp gives off a rich fragrance of tropical punch and tastes the same way, and blue passionflower fruit has a vaguely blackberry-like flavor that stands in for blackberries in a pie.
The myth: Caterpillars eating the leaves will kill the vine.
The reality: They slow the plant down as they work through the foliage, and it survives.
The myth: Aphids on the new growth are the pest to worry about.
The reality: Aphids are not recognized as a primary pest on passion fruit and seldom cause serious damage on their own, but they are the main way woodiness virus moves from plant to plant.
The myth: A passionflower needs a big pot before it will flower.
The reality: Blue passionflower will flower in a small pot, though it does better where there is plenty of root space.
What to expect, year by year
An honest picture of the first three seasons, which is where most of the disappointment with this plant sits.
Year one is establishment and very little else. A vine planted in spring spends the season making stems, tendrils and root, and it may not flower at all in its first summer. Fruit is unlikely whatever you do, because the plant is not old enough for it yet. The work is a support the tendrils can catch, water that keeps the plant from wilting, and restraint with the fertilizer bag.
Year two is when the plant shows what it is. Growth starts earlier and runs harder, flowering fills the summer, and the first fruit becomes possible if bees or your own brush have done the work. This is also the season the first shoots appear at a distance from the crown, so a standing habit of removing root suckers belongs here, while they are still young enough to pull by hand.
From year three the plant is on a maintenance cycle, and the annual spring tidy does most of the work. Expect to walk the bed each spring pulling suckers, expect the top to be replaced from the roots in cold zones and to thicken into a woody framework in warm ones, and expect the plant to outlive the trellis you gave it.
Flower photos
FAQ
Is passionflower hardy in zone 6?
The hardy species are. Maypop is rated zones 5 to 9, yellow passionflower runs 5a to 10b, and blue passionflower is rated 6a to 10b, with a narrower listing of zones 7 to 9. Expect the top to die back and the plant to return from the roots.
Do passion flowers come back every year?
Hardy species do. Maypop dies to the ground in cold winters and returns from the roots, and the roots of blue passionflower have come through a hard freeze with the top killed. Tender species have no such reserve, since they need a minimum of 41 to 45 degrees Fahrenheit.
Why does my passion flower vine flower but not fruit?
Pollination, most of the time. The anthers sit below the stigmas, so the flower needs an insect or a brush, and wind does not help because the pollen grains are heavy and sticky. Maypop adds self-incompatibility: in a controlled trial, none of 122 self-pollinated flowers set fruit.
Can you eat passion flower fruit?
The ripe pulp of several species is eaten. Ripened maypops go straight off the vine or into jelly, and blue passionflower fruit is edible though it tastes bland. The leaves and stems are the parts that carry cyanogenic glycosides.
Is passionflower poisonous to dogs and cats?
It is listed as a problem for cats, dogs, horses and children, with poison severity rated medium. The recorded symptoms are severe nausea, vomiting, drowsiness and episodes of irregular heartbeat.
How do you cut back a passion fruit vine?
Once a year in early spring, taking out the old flowered stems. Routine cuts take flowered shoots back to two buds from the previous year's framework.
What do you do with passion flowers in winter?
In the hardy range, mulch the root zone and wrap any stems you want to keep with insulating fleece. Leave the dead top standing until spring so the brown pupae hanging on it are not thrown out with the stems. Tender species come indoors before the cold arrives.
Is a maypop the same thing as a passion fruit?
They are different species. Maypop is Passiflora incarnata, native to the southeastern and south-central states and hardy well into cold-winter country. The grocery passion fruit is P. edulis, native to Paraguay, Brazil and Argentina and winter hardy only in zones 10 to 12.
Can you grow maypop in a container?
Yes. Start a young plant in a pot about 12 inches wide and repot every two or three years.
What does passion flower do to your body?
It has traditionally been used as a sedative and is promoted for anxiety, sleep problems, stress, attention-deficit hyperactivity disorder and pain, though its effect on anxiety and other conditions has not been studied extensively. Reported side effects are drowsiness, dizziness and confusion.
Is it safe to take passionflower every day?
Passionflower tea may be safe for up to 7 nights, and daily use of passionflower extract may be safe for up to 8 weeks. It is advised against in pregnancy because it may induce uterine contractions, and it may interact with anesthesia drugs, so it is avoided before surgery.
Interesting tips
- The white blue passionflower is catalogued under two spellings, 'Constance Elliot' and 'Constance Eliott', so a nursery search that comes up empty is worth running again the other way.
- Where collar rot has taken a passion fruit vine, the fungus behind it stays viable in that soil for up to four years, so the replacement plant goes somewhere else in the garden.
- Silken webbing over the leaves is the sign that a mite population has already gone dense, which is why an indoor vine gets checked underneath the leaves and not only over them.
Related Guides & Flowers
Wisteria
The other climber that outgrows its trellis and lives or dies by when it gets pruned.
Jasmine
The other climber people put on the same fence, grown for scent and with its own winter problems.
Meaning of flowers
What other flowers have come to stand for, and where those readings started.
Types of flowers
The full catalog of flowers grouped by kind, for whatever goes on the trellis next.