In season: passiflora

Spanish monks first discovered passiflora in Mexico in the early 17th century and sent back drawings of the plants to Europe, where, in Rome, Giacomo Bosio, a monastic scholar, saw them as symbols of Christ’s passion. First classified by Linnaeus in 1745, passion flowers were a motif of Arts and Crafts textiles in the 1880s, and of 1920s Art Deco pottery, and continue to be loved by botanical artists for their distinctive flower shape and tendrils.

Popular with plant collectors, amateur and professional, new hybrids of these intricate flowers are being developed all the time. John Vanderplank, who holds a National Collection of passion flowers at Butterfly House in Somerset, concentrates on the scientific side to ensure that a complete and accurate record is kept of passion flower introductions.

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Butterfly House
RHS Garden Wisley

The rampant Passiflora caerulea, the most common passion flower in Britain, will cover a good large area of a fence or wall. For new collectors, National Collection holder Jane Lindsay, of Tynings Nursery, recommends you begin with the hardy Passiflora caerulea. With reddish purple sepals and petals and banded white filaments, P. alata is a scented climber for the conservatory. A cross between caerulea and alata, P. x belotti is also a strong-scented, vigorous flowerer that thrives in a conservatory.

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Tynings Nursery, open by appointment only

P. ‘Amethyst’, ‘Victoria’, ‘Iris’ and ‘Betty Myles Young’ are hardy if planted in a very sheltered spot. Most passion flowers only open for a day, apart from the Australian ones, such as P. aurantia, which bloom in a cool greenhouse for three to four days, going from very pale to a much deeper orange.

Native to central and south America, this passion flower has thin, wiry, woody stems and bracts which serve as insect traps. Hardy to 30°F/-2°C, it favours more damp conditions than some.

This passion flower is self-pollinating and is the most common provider of the passion fruit you will buy to eat. For good fruit, also consider growing P. mollissima, which has pale pink pendulous flowers and a long thin yellow ‘banana’ fruit. Both do well if overwintered in a cool greenhouse.

Half-hardy Passiflora ‘Betty Myles Young’ can be grown outside as long as it is in a very sheltered position; it will flower for 10 months of the year in a conservatory.

• Plant hardy passion flower plants such as Passiflora caerulea in shallow, well-drained soil near a house, fence or garage wall.
• Make sure the old compost is level with new soil.
• In summer, give plants a good bucketful of water every three or four days rather than a light, daily sprinkle. Note, however, that wet as much as cold is the enemy of passion flowers, so make sure that their roots do not sit in water.
• If growing from seed, germinate in compost at a constant temperature of 79°F/26°C.
• Reduce temperature after germination to 60°F/16°C before potting in a soil-based mixture of sharp sand, gravel and loam.
• Pot up in stages and do not overfeed; like agapanthus, passion flowers do best if their roots are tightly compacted.

• Use a well-balanced fertiliser, such as tomato food, once every week or 10 days, and apply to the roots.
• It is worth repeating, be careful not to overfeed as it will simply encourage lush foliage instead of flowers.
• If your passion flowers are not self-pollinating (P. edulis is, P. incarnata is not), put two plants in one pot.
• Blue, white and purple passion flowers tend to be hardier; if they are red, they are not hardy but need to be overwintered in a conservatory or greenhouse.
• Leave the old, unsightly foliage over the winter and prune lightly once the new growth starts in spring.