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A blue passion flower seen from the front, with white petals and a ring of blue and purple filaments

Passion flower

Passiflora caerulea
Care level: Easy

The blue passion flower is a fast, evergreen to semi-evergreen climber from South America and the hardiest of its large tropical family. Its flowers look engineered: ten white petals, a ring of filaments banded in blue, white and purple, and a raised centre of five green anthers and three dark stigmas. They open from summer into autumn and are followed in warm years by orange, egg-shaped fruits. It climbs by tendrils on wires or trellis against a warm, sheltered wall and regrows from the base if a hard winter cuts it down.

I have this plant
Varieties and related species
Passiflora caerulea 'Constance Elliott'Passiflora edulisPassiflora incarnata

Light

Full sun or light shade, with shelter from cold wind. A south- or west-facing wall is ideal.

Water

Water regularly in the first year and in dry spells. Plants in pots need water often in summer.

Humidity

Not a factor outdoors. Under glass, dry air encourages red spider mite.

Soil

Moderately fertile, well-drained but moisture-holding soil of any type.

Size

8-12m as a climber on a wall or fence; kept smaller by pruning or in a pot.

Growth speed

Fast

Hardiness

Hardy down to about -10°C. Source: RHS

Toxic to pets

Toxic to cats and dogs if eaten.

Can cause vomiting and diarrhoea, and more rarely affects heart rhythm.

If your pet has eaten some, contact your vet.

Source: NC State Extension

Signature feature

Each flower lasts only about a day, but a healthy plant on a sunny wall opens new ones daily from midsummer to early autumn. The ring of coloured filaments, the corona, is what sets passion flowers apart from every other climber.

Spring

Prune once the worst frosts are past and tie in new shoots as they grow.

Summer

Flowers open daily. Water in dry weather and guide the fast growth onto its support.

Autumn

Flowering tails off and orange fruits ripen in warm years. Mulch the roots.

Winter

Leaves may drop in the cold. Protect the base with mulch, and move potted plants under cover.

Planting

Plant in spring at the foot of a warm, sheltered wall or fence, about 30-45cm out from the base, in well-drained soil. Fix wires or trellis first.

Fertilising

A general fertiliser in spring is enough in the ground. Feed potted plants every few weeks in summer, but avoid heavy feeding, which gives leaves rather than flowers.

Pruning

In early spring remove dead and frost-damaged stems and shorten side shoots to two or three buds from the main framework. Cut out overcrowded growth.

Support

Give wires, trellis or mesh for the tendrils to grip, and tie in the main stems to spread them out.

Propagation

By semi-ripe cuttings in summer, by layering in spring, or by lifting rooted suckers.

Common problems

Plenty of growth but no flowers

Most likely cause: Shade, rich soil or too much fertiliser.
What to do: Move a potted plant into full sun and stop feeding.

Stems brown and dead after winter

Most likely cause: Frost damage.
What to do: Wait until spring, then cut back to live wood or to the base; it usually reshoots.

Leaves yellow and fall in winter

Most likely cause: Cold weather.
What to do: Normal for a semi-evergreen; new leaves follow in spring.

Shoots coming up away from the plant

Most likely cause: Suckers from the roots.
What to do: Pull or dig them out as they appear.

Flower buds drop

Most likely cause: Dry roots or a sudden cold spell.
What to do: Water deeply and mulch.

A tangled mass of stems

Most likely cause: No annual pruning.
What to do: Thin out and shorten the side shoots each spring.

Pests & Diseases

Red spider mite

Signs: Fine pale speckling on the leaves and thin webbing, mostly on plants under glass in warm, dry air.
Treatment: Raise humidity, rinse the foliage and ventilate well. Check the undersides of the leaves and the crevices where the leaf stem meets the main stalk.

Mealybugs

Signs: White, woolly tufts in the leaf joints and along the stems of plants under glass.
Treatment: Dab them off with a cotton bud dipped in alcohol and repeat weekly. Check the undersides of the leaves and the crevices where the leaf stem meets the main stalk.

Whitefly

Signs: Clouds of tiny white insects that fly up from plants under glass when touched.
Treatment: Hang yellow sticky traps and rinse the undersides of the leaves.

Scale insects

Signs: Small brown bumps on stems and under leaves, with sticky honeydew.
Treatment: Scrape or wipe them off and prune out badly affected stems.

Is the blue passion flower hardy?

Hardy enough for a sheltered wall in mild regions, down to about -5 to -10°C. In a hard winter the top growth can be killed, but an established plant usually shoots again from the base in spring. Mulch the roots in autumn.

Can you eat the fruits?

The orange fruits are edible when fully ripe, but they are seedy and bland. Unripe fruits can upset the stomach. The passion fruit sold in shops comes from another species, Passiflora edulis, which needs warmth under glass.

Why is my passion flower not flowering?

The usual causes are shade, rich soil or heavy feeding that produce leaves instead, and a young plant still settling in. Give it the sunniest wall you have and do not overfeed.

When and how should I prune it?

In early spring, after the worst frosts. Remove dead and frost-damaged stems and shorten the side shoots to a couple of buds from the main framework. Trim again lightly after flowering if it has outgrown its space.

Is it invasive in the garden?

It can be a nuisance. In a warm spot it sends up suckers some distance from the plant and grows very fast. Pull the suckers out and prune every year, or grow it in a large pot.

Can I grow it in a pot?

Yes, in a large container with a support, and that is the best option in cold areas: move the pot under glass or into a bright, frost-free place for winter.

Why are the leaves yellowing or dropping in winter?

Cold. It is only semi-evergreen and sheds leaves in a cold spell. New leaves follow in spring.

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