How to care for passion flower and other exotic climbers

As far removed from an English cottage garden as you can travel, the passion flower (Passiflora) is one of the most theatrical and exotic of plants. The weird and wonderful blooms are embellished with many showy parts that together remind you of peering into a kaleidoscope as a child: in the centre, the anthers, stigmas, and ovary protrude over the filament rays, which are marked with circles of incredible colour.

This peacock of flowers hails mainly from the Neotropical realm of Central and South America, where it grows in mountainous terrain and rainforest. It is a rampant evergreen that uses tendrils to either climb or scramble along the ground or through thickets. The genus comprises around 600 species, which bloom in shades of purple, blue, yellow, red, or white and produce fruits. Passiflora edulis is the most edible and widely cultivated for its fruit juice, while the foliage, roots, and fruit of some species are used in herbal and folk medicine as a sedative or to induce hypnotic euphoria. Passion flowers are pollinated by a range of wildlife, including bees, bats, and hummingbirds, and have a fascinating symbiotic relationship with ants, who feed on the plants and protect them from predators.

Passiflora were introduced to Europe in the eighteenth century and became popular with the Victorians, who grew hybrids of them in gardens and hothouses. Being tricky to cultivate outdoors, they fell out of favour, but have enjoyed a surge in popularity in recent years, as gardeners look for exotic plants to create jungle-style borders and the climate warms.

The name is said to relate to the crucifixion, since passion stems from the Latin passio, meaning suffering. Spanish missionaries in South America during the 15th and 16th centuries regarded the flower structure as a symbol of the passion of Christ. At first glance, it seems rather a long stretch, but the filaments are supposed to represent the crown of thorns, the ovary is the holy grail, the ten petals are the apostles (minus Judas and Peter), the stigmas are the nails on the cross, the stamens are the five wounds, and the tendrils are the whips used on Jesus. The Japanese and Greek name for Passiflora – clock plant – is a lot more obvious, since the blooms do look like clock faces. Some species have such long filaments above their petals that they resemble marine life: P. actinia is known as the sea anemone passion flower, and, if you saw P. quadrangularis underwater, you could mistake it for a jellyfish. In India, the blue species are known as Krishna’s flower, since the mesmerising purple-blue hue of the filaments is the colour of the Hindu god.

The majority of passion flower species are tender and therefore, in the UK, fare best in a conservatory or greenhouse. However, there are a few that will grow outside in urban areas and milder regions, tolerating -8°C. The most widely available is the blue passion flower (Passiflora caerulea), which has ivory petals and rings of purple-blue filaments; these blooms are produced throughout summer and into early autumn and followed by egg-shaped orange fruit, which are edible but bland. Very similar, but with bigger, better flowers is the robust hybrid ‘Damsel’s Delight’.

For even more colour, ‘Rubra’ is red magenta with a white necklace of filaments; ‘La Morellina’ boasts pink-violet petals and blue filaments; and ‘Betty Myles Young’ is an amethyst flower with a black, white, and blue heart. Alternatively, for more subtle exotica, ‘Constance Eliott’ has gorgeous white and cream flowers with a green centre, and ‘Snow Queen’ is similar, but hardier with much larger blooms.

For outdoor growing, choose a sheltered warm wall, ideally in a south or west-facing position. Passion flowers like their feet in very free-draining soil, so dig in sand or gravel, if necessary, before planting. For the best results, plant in spring.

For those on heavy soils (such as clay), passion flower breeder Myles Stewart Irvine (who has raised the resilient Riverside hybrids, including ‘Damsel’s Delight’ and ‘Snow Queen’) recommends potting up young plants in large, deep containers for their first summer to encourage good root growth and overwintering them indoors, before planting out the following year.

Yes, but being (potentially) big climbers, they may need repotting several times. It’s vital not to start off with an overly large container, if you intend to keep your passion flower as a pot plant – for instance, on a roof terrace. This is because they dislike rich, damp soil. Therefore, opt for a pot that is slightly larger than the container you purchase the plant in, use a mix of compost and grit, and enhance drainage further by sitting it on pot feet.

Yes, in the milder parts of the UK. Allow your passion flower plenty of space because, in favourable conditions (such as a sheltered, sunny garden in London), it will be vigorous – capable of 25 metres. If you need to prune it, wait until growth begins in spring and don’t be too ruthless: for example, as when pruning a rose, avoid cutting back the main stems.

Use a general fertiliser (such as Vitax Q4), but don’t overfeed – one dose per year is sufficient. Too much food, especially nitrogen-heavy forms, can hamper flowering.

The seven passion flowers recommended above should survive temperatures down to –5-10°C. If you live in a very cold area, where winter temperatures plummet below that, it would be better to grow passion flower in a heated conservatory or greenhouse. Since it is the cold and wet of winter that can cause the roots to rot, plants outdoors should be mulched well (for instance, with bracken or straw) or the base covered with horticultural fleece or both, in autumn. Plants indoors benefit from heat around their roots – for example, via a heating cable running through the soil or compost. Give passion flowers the protection they need during the winter months, and they will fill the garden with the exotic verve of the tropics all summer long.

JASMINE fills the air with delicious exotic scent. The large-flowered Jasminum officinale f. affine is stunning. Star jasmine (Trachelospermum jasminoides) has a tea perfume and glossy leaves that redden in winter. Both enjoy a sheltered, sunny wall.

CHOCOLATE VINE (Akebia quinata) has maroon flowers with a spiced-vanilla aroma in spring, followed by purple sausage-shaped fruits. It is semi-evergreen and hardy on a sheltered wall in most parts of the UK.

NASTURTIUMS always look tropical and the annual forms are easy. Of the perennials, the most resilient is Tropaeolum speciosum, which blazes vermillion red in summer and autumn; hardy in most parts of the UK, it likes its feet in cool shade and its top in sunshine.

DUTCHMAN’S PIPE (Aristolochia macrophylla) is a twining vine with heart-shaped leaves and tropical-looking mottled pink-brown flowers in summer. It is hardy, but prefers a sheltered site.

MORNING GLORIES are annuals, but well worth growing for their summer blooms, which look like they belong in a jungle. Ipomoea tricolor ‘Heavenly Blue’ produces azure trumpets, whilst the Spanish flag (Ipomoea lobata) has ladders of red, orange, and cream flowers that look like flames.