Passiflora (passion flower) is an evergreen climber with exotic looking flowers, sometimes followed by brightly coloured fruits. Suited to a sunny sheltered spot in mild regions of the UK, in colder areas it can be grown under cover of a greenhouse or conservatory.
Passion flower likes moderately fertile, well-drained but reliably moist soils. It will thrive in any soil type and is not fussy about acidity or alkalinity.
Full sun or dappled shade is best, with shelter from cold, drying winds. A south, south-west or west-facing wall is ideal.
If growing passion flower in a south-facing glasshouse or conservatory, shade from direct sunlight may be needed to prevent the leaves from scorching.
Passion flower can also be grown in a container. Use either John Innes No 3 potting compost, or good quality multipurpose or peat-free compost.
Watering and feeding
Water passion flowers freely during the growing season (especially container grown specimens) to ensure that they don’t dry out. Water them more sparingly during the winter, allowing the compost surface of container grown specimens to begin to dry out between waterings.
Top dress garden specimens with a general fertiliser such as Growmore, Vitax Q4 or blood fish and bone using the application dose on the packet (or 50-70g per sq m (1½-2oz per sq yd) if no dose is given).
The hardiness of passion flower varies between species and cultivars:
- Passiflora incarnata is fully hardy, but should still be grown in a sheltered spot
- P. caerulea is frost hardy, so is suitable for outdoor growing in milder regions of the UK only, and may require some winter protection
- P. mollissima, P. × exoniensis, P. antioquiensis, P. x alatocaerulea, P. × allardii, P. × caeruleoracemosa, P. manicata and P. alata require a minimum temperature of 5-7°C (41-45°F) so are best suited to glasshouse or conservatory conditions
Other species, including P. edulis (the passion fruit or granadilla), P. coccinea, P. racemosa, P. vitifolia and P. quadrangularis require tropical conditions and minimum temperatures of 10-16°C (50-61°F), depending upon the species. Their cultivation is not dealt with here.
Edibility of fruit
P. edulis is the species grown, in warmer climates, for its edible fruit.
The relatively winter-hardy Passiflora caerulea often produces egg-shaped orange fruits in warm Britih summers. They can be eaten when fully ripe, but please be aware that under-ripe fruits (yellow) can cause stomach upsets.
All other parts of the Passiflora plants are potentially harmful and should not be eaten.
Pruning and training
Although Passiflora is a self-clinging tendril climber, it benefits from fan-training, which produces a more attractive plant than if left alone to scramble. For a step-by-step guide to fan training against a wall or fence, see our page on training and pruning climbers on first planting.
Carry out pruning just after flowering by shortening flowered tips and sideshoots to a couple of buds from the main fan framework.
If your passion flower is overgrown or frost-damaged plants, carry out renovation pruning in spring by cutting back the stems to 30-60cm (1-2ft) from soil level. Cut to a bud or side shoot wherever possible. The plant will respond by sending out lots of new green shoots. These will need thinning out and formative training. Flowering will be reduced for a year or two.
Like most climbers, passion flower can be layered in spring, but also take well from softwood cuttings in spring or semi-ripe cuttings in summer.
Species plants (but not named cultivars) will come true from seed. You will know if your passion flower has produced seed, because the ovoid yellow-orange fruits in late summer or autumn are hard to miss! Incidentally, these are edible when fully ripe, but unrewarding compared to the passion fruit sold by grocers, which are fruit of the tropical species Passiflora edulis. See the section on Edibility of Fruit above for more details.
Seed sowing technique:
- The fruits should be allowed to ripen and then stored ripe for 14 days, indoors on a tray. The fruits will start to ferment, a process that helps to kill off spores of the fungal disease Fusarium, which otherwise can cause seedlings to damp off and rot
- After 14 days, mash the fruits into a pulp and leave this in a warm place to ferment further for three days
- Push the pulp through a sieve under running water to separate out and clean the seeds, ensuring that they are pulp-free
- Allow them to dry before pouring hot water from the kettle over them in a bowl, and leave them overnight to soften their hard seed coats. Do not leave them longer, as they may rot
- Seeds should then be sown immediately, following our advice page on shrub-seed sowing
Passiflora is prone to plant viruses, especially Cucumber mosaic virus, and aphid damage.
When grown under glass, Passiflora is susceptible to common greenhouse pests such as red spider mite, whitefly, scale insect and mealybug.
Wind scorch and cultivation problems are common (as with all garden plants), particularly during spells of cold weather or when growing conditions are less than ideal.