Passionflowers have an unparalleled ability to transport us to exotic places, each flower drawing you in with its hypnotic complexity. Grow them and these wonderful things climbing mountant man will add excitement and bring a sense of curiosity to our garden and Greenhouse.
These attractive climbers can be found in the wild in rainforest environments across North and South America, Africa, Asia and Australia, fighting their way through the canopy of trees and shrubs, using their tendrils to reach the ‘Emerald City’ – the shaded part where sunlight reaches. Although native to the tropics, passionflowers are remarkably tolerant of subtropical and temperate climates, allowing us to grow many species here in the UK.
Passionflowers were introduced to Britain in the 18th century, and by the early 20th century passionflower craze had reached its peak as species were also imported from Australia. Wealthy households who had grown these wonderful tropical plants in their heated greenhouses found that the onset of World War I meant they needed to divert their money elsewhere. It was only relatively recently, as Western wealth recovered, that the passionflower revival began.
Most passionflowers are hardy climbers, making them perfect for growing on fences and trellises in our gardens and for adding fragrance and mystery to conservatories and greenhouses. Despite their incredibly attractive flowers, they are easy to grow: outdoor varieties grow best in sheltered areas, while tropical species, which need a minimum temperature of 10°C at night, grow best in a conservatory or greenhouse.
Passiflora caerulea is most easily recognised when grown outdoors in a sheltered location and can survive temperatures as low as -9°C. Just remember that a strong, established root system and well-drained soil are essential for the plant to withstand such harsh conditions. Choose the right location – the south-facing wall of the house is ideal as it will provide some protection over winter and could make the difference between your plant surviving and thriving.
With the Award of Gardening Merit from the RHS, P. green is the best known and widely grown species for a reason. A large number of blue and white flowers appear in the summer, followed by orange fruits about the size of a hen’s egg. At its peak, it will grow to around 8m tall.
The cultivars ‘Amethyst’ and ‘Constance Elliot’ have both won Awards of Horticultural Merit. ‘Amethyst’, which grows to 4m tall, produces brilliant purple flowers from July to September. Suitable for a south-facing wall but may need a little protection in more northerly areas.
‘Constance Elliot’ produces white star-shaped flowers from late summer to autumn on plants up to 8m tall. They are rich in nectar and are particularly attractive to pollinators.
If your garden is sheltered or you live in a temperate area, consider P.x violet. This is one of the oldest known hybrids, blooming purple from June to September and can grow well in an unheated greenhouse or a sunny, sheltered spot in the garden.
The same goes for plant varieties. P.x violet ‘Eynsford Gem’, which you could also try growing in a winter hardy pot. Growing up to 6m tall, it has pink to pale purple flowers with white threads and semi-evergreen foliage depending on location and winter temperatures.
Greenhouses and conservatories provide the perfect opportunity to grow more showy flowers. Most passionflowers will happily overwinter in high light and warmth, but overwintering the more delicate flowers can be a challenge in cooler conditions. Insulation, good air flow and soil that is kept dry will help your vines to overwinter successfully.
Among my recommendations for greenhouses or conservatories are: ‘Sunburst’, which has profuse orange to yellow flowers along with interesting variegated foliage, growing to 5m tall; a more compact form which flowers sporadically all year round but needs good light levels in winter, producing tomato red to orange flowers; and ‘Curiosa’, which has attractive showy foliage and small cream to green flowers, requiring a minimum temperature of 5°C.
Australian species Passiflora aurantia Known as the two-tone passionflower, it has white buds and young flowers that turn deep orange-red with age. It may not like to flower under glass if overfed and will grow to 5m tall. For containers in a partly shaded position in a greenhouse or conservatory, consider ‘Anastasia’, which has large pink flowers on a more compact plant that grows to 3m tall.
Whether grown indoors or outdoors, when it comes to soil, most passionflowers do not like heavy, waterlogged conditions and prefer sandy, well-drained soil that is not too fertile. Slightly alkaline soil is ideal, but neutral to slightly acidic soil will do. For those with heavy soil, a raised bed with plenty of sand in the mix will work, or consider a pot with good drainage and gravel in the compost mix.
Trevor Triggs and Kevin Bosustow, owners of Cross Common Nursery in Cornwall, advise against potting passionflowers too large. “A lot of passionflowers die from over-potting and root rot, they don’t mind being a little restricted. When using peat-free compost, watering and fertilising is generally more frequent – half a dose of liquid seaweed with each watering in the summer will help,” they say. Once established, most passionflowers are deep-rooted and drought-tolerant.
The art of training passionflowers is to work little and often. Continue tying on new growth to cover the trellis, pole or shrub you have chosen and remove the tips of the shoots once they have reached the desired height. This encourages more flower-bearing side shoots to develop, which will bloom in the summer.
Pruning is best done in the spring when the harshest winter weather has passed and the buds are opening to signal the sap is rising. Most pruning is to keep the passionflower in its allotted space, but take this opportunity to remove any dead branches in the spring and some old wood to encourage new growth.
Passionflowers grown outdoors have relatively few pest and disease problems, except for the occasional slug that damages young plants. Growing under glass can increase the risk of problems, so be vigilant and keep an eye out bug number of mealybugs and Red spiderespecially near the tips of shoots where the tissue is soft and tender. Mildew can be a problem when growing in greenhouses or conservatories, so prevent such attacks by maintaining good air circulation and increasing humidity, especially on warm days.
first. F. White Mountain Guinea Pig
This elegant cup and saucer shaped vine grows vigorously and interestingly, reaching heights of up to 3m. Grow as a seeded annual or overwintering perennial.
2. Dregea sinensis
Fragrant hoya-like flowers appear between felt leaves, growing up to 3m tall. Needs well-drained soil, part shade and sheltered location.
3. Eccremocarpus scale plant
An exotic looking vine that flowers continuously throughout the summer. Perennial in sheltered areas, can be grown from seed each year.
4. Schizophragma hydrangeoides ‘Moonlight’
Related to hydrangeas, green leaves and cream flowers, up to 10m tall.
5. Solanum laxum ‘White’
This semi-evergreen vine is covered with jasmine-scented white flowers in summer. Fast growing in sheltered areas, reaching heights of up to 12m.
6. A beautiful trophy
A delicate perennial called flame cress. It thrives in cool climates and is particularly useful when grown in a yew hedge, growing up to 3m high.
