Passiflora caerulea Clear Sky- Passion Flower

The Passiflora caerulea 'Clear Sky', also known as passionflower or blue passion flower, is a vigorous perennial climbing plant, reasonably hardy, semi-evergreen, clinging to its support thanks to its tendrils. Throughout the summer, it produces flowers slightly paler than the species but larger and more resistant to full sun. They have an exotic and graphic appearance that leaves no one indifferent. White-blue in colour, adorned with a collar of tricoloured filaments, light blue, white, and purple, they are followed after a hot summer by orange fruits, edible but tasteless. This highly decorative rambler displays an excellent resistance to frost. It should be grown in the sun, in well-drained ordinary soil, even limestone.

Primarily native to tropical areas of South America, Passiflores belong to the family Passifloraceae, of which they are the most widespread genus, with the others being known only to collectors. There are more than 500 species of Passiflora, as well as numerous spontaneous or horticultural hybrids. They are mostly tropical plants, but some species are subtropical and can survive winter in mild and sheltered areas. Passiflora caerulea is one of the hardiest, capable of withstanding temperatures as low as -12 °C (10.4°F), and therefore is probably the most commonly planted.

'Clear Sky' is a tetraploid variety (meaning it has twice the normal number of chromosomes) obtained by German breeder Roland Fisher. Polyploidy (multiplication of the chromosome stock) enhances certain desirable traits in plants. Starting with a cross involving the Emil Kugler variety, Dr. Fisher obtained 'Clear Sky', which has larger flowers than the botanical blue passionflower. Clear Sky's flowers are also paler and more resistant to full sun. This climbing plant reaches a height of 3m (10ft) and a width of approximately 1.50m (5ft), but it can grow taller in favourable climates and without pruning to limit its growth. Its beautiful deep green foliage, deeply lobed, is semi-evergreen, meaning it falls off in cold winters but remains evergreen in mild climates. The flowers have the same sophisticated structure as the botanical species, with ten petals and sepals that look similar but are whiter. The decorative crown of filaments in Passiflores is dark purple at the base, then white in the middle, and light blue at the tip, vaguely resembling a British cockade... The central sexual floral parts are green and yellow for the stamens and purple striped for the pistil, contrasting the white petals and sepals. This highly sophisticated floral ensemble contributes to the fascination exerted by this plant, which has been associated with the passion of Christ for several centuries, with each floral element having its specific meaning (the Apostles, the nails of the crucifixion...). In Clear Sky, the flowers are very large, reaching a diameter of 11cm (4in), and bloom from May to October. If the summer is hot enough, they develop into decorative orange egg-shaped fruits, edible but tasteless.

The 'Clear Sky' passionflower is a fast-growing, rambling plant that clings to its support with tendrils. The well-protected stump of this passionflower can withstand temperatures as low as -8 °C (17.6°F) to -10 °C (14°F). It can be grown in a container in colder climates to protect it during winter.

If your climate allows planting it in the ground, know that it thrives in most soils (pH 5.6 to 7.8), slightly moist but well-drained for winter survival. Remember to water it in the summer in Mediterranean coastal climates.

The blue 'Clear Sky' passionflower is perfect for covering fences, trellises, unsightly fences, or old sunny walls in the south or west. Provide it with a sheltered position away from winds. It is an excellent companion for other climbing plants. To enhance the exotic aspect of this passionflower, pair it with Campsis capreolata (or Bignonia capreolata), a vine with stunning red and yellow trumpet-shaped flowers that smell like chocolate! The Jasminum officinale, with its intoxicating perfume, will also be a perfect companion to complete this tropical-looking scene in mild temperate climates.