passionfruit

Passionfruit provide us with a taste of the tropics in late summer and autumn, arriving at the tail end of the stone fruit season and just before the apples, pears and feijoas arrive in full force. The passionfruit of my childhood were not of the regal purple-skinned variety commonly seen on the supermarket shelf, but the hardier (these days classified as rather too hardy) banana passionfruit (Passiflora mixta) – well before they attained their current noxious weed status. We would harvest the long yellow fruit with their spongy-soft skin from roadsides in the Marlborough Sounds, using a tool my Dad made expressly for this purpose (comprised of a tin can, a broom handle and some retired pantyhose). We even had a vine covering the front of our house, such was our passion for this fruit. Every now and again, a stray tendril would find its way under the eaves and inside the house…where there’s a will, there’s a way!

Standard purple passionfruit can be grown successfully in the home garden in warmer parts of the country, but truth be told I think they are one of those crops that either do very well for you (basically thriving on neglect or something close to it), or are a complete failure, year in year out, no matter what you throw at them. I am one of the gardeners whose experiences fall into the latter category, so let’s have a crack at learning together what makes these glossy green vines tick.

Passionfruit: a short family history

The passionfruit we are most familiar with belong to the genus Passiflora, a group of 500-550 species of vigorous, evergreen vines belonging to the Passifloraceae family. Most originate from the Americas, with a handful of species found in Southeast Asia and Oceania (New Zealand has its own native passionfruit, kōhia (Passiflora tetrandra) which has small (30 mm in length) bright orange fruit). About 10% of Passiflora species have palatable fruit. The fruit received its common name via missionaries visiting South America from the 1500s onwards – much religious symbolism is associated with the structure and componentry of the flowers (see footnotes at the end of this article for more detail). The missionaries also learned of the soporific qualities of the passion vine from the indigenous tribes of South America, and its value as a natural sedative when taken as a tea or supplement spread with the introduction of the vines across Europe and further afield.

Many Passiflora species are grown because of their highly ornamental nature, with a wide variety of ornate, showy flower structures and brilliant colouring. The species most commonly grown as an ornamental is Passiflora caerulea, the bluecrown passionflower.

Purple passionfruit (Passiflora edulis) are now cultivated in tropical and subtropical regions worldwide and are grown commercially in Australia and New Zealand, Hawaii, South Africa and Brazil. Purple passionfruit are native to southern Brazil through Paraguay to northern Argentina. There is a gold-skinned variant (Passiflora edulis var. flavicarpa), which isn’t a botanically distinct species from standard purple passionfruit, but is nowhere near as vigorous or hardy and said to have differing climatic preferences. These vines bear slightly larger fruit with a bright yellow skin and the pulp tends to be slightly tarter than that of purple fruit. It is thought that the gold form is of unknown origin, but potentially a native of the Amazon region of Brazil. Although widely known as yellow passionfruit, the fruit goes by a number of more exotic monikers: golden passionfruit in Australia and New Zealand, yellow lilikoi in Hawaii, and parcha amarilla in Venezuela.

Suitable climates and growing conditions

These somewhat finicky frost-tender vines are best treated as subtropicals and as such, will grow throughout the North Island and top of the South Island without too much trouble. In frost-prone areas, you could try tucking a plant under the eaves of your house where it can benefit from some shelter and morning sun. A commercial grower I visited several years ago used hail cloth to enclose his vines, giving about 2°C temperature protection.

Given the right conditions, passionfruit vines can grow to quite a large size. If you are growing more than one plant, it is advisable to allow approximately three to four metres between plants. Providing a trellis or similar framework for the vines to grow up will prevent them from turning into a tangled mess – try wooden trellising (1.8 – 2 m high, allowing about three metres in length per plant) or grow them overhead on a pergola.

Passionfruit plants are not particularly long-lived, so expect to replace your plants every five or so years. As they age, their structure becomes increasingly woody and unproductive. Passionfruit flowers are insect pollinated (usually self-fertile, but some yellow variants have self-sterile flowers, requiring cross-pollination) and although they will flower in the rain, bees won’t pollinate wet flowers. Warm temperatures are required at flowering time for successful pollination. The fruit is borne on the current season’s growth (60-80 days from fruit set to maturity) and the fruit is best picked up off the ground rather than off the vine.

Plants can be propagated by seed (sow this fresh for best results, you can ferment the seeds in water for 48 hours to remove the pulp first). Sow in potting mix at a depth of approximately 1 cm, germination should take place within 10-20 days. You can also take cuttings in late winter to spring (young green material), or semi-hardwood cuttings from vegetative stems in summer. A dip in rooting hormone is advised, and they should root in three to four weeks, but in reality, this can take up to eight or nine weeks. You can also purchase grafted nursery-grown plants with the added benefits of disease resistance and enhanced pollination conferred by specialist rootstocks.

Site selection and planting

Plant passionfruit vines in spring, once the danger of late frosts has passed. Choose a warm, sunny, sheltered position – protection from the wind is important. If growing against a wall or side of the house, choose a place that receives morning sun but not strong afternoon sun, as excess reflected heat may stress the plant (they will tolerate a little shading).

Well-drained, preferably fertile soil types are a must, as passionfruit vines are highly susceptible to waterlogging and root rots. I have read many posts online where someone’s passionfruit plant has curled up and died seemingly overnight and I wonder how many of these situations are due to overwatering, waterlogging and related soilborne diseases.

Culture and care

Adequate moisture via irrigation at planting and during the summer growth period is a must to ensure a good passionfruit crop and is particularly important if you have a vine under the eaves of your house, where the soil can be drier. Lack of water can cause fruit to shrivel prematurely on the vine. Regular irrigation prolongs the duration of flowering and fruiting.

Passionfruit have reasonably high nutrient requirements, so small, regular applications of fertiliser throughout the season are ideal. Start with the addition of blood and bone or good compost to the planting hole at establishment, followed by an application of general compound fertiliser (100 g/square metre) in early spring and at least once again in summer – the commercial grower I visited used general fertiliser initially, then an application of about a handful of citrus fertiliser per vine prior to rain during the growing season. You can also apply foliar feeds in the form of humates, fish or seaweed solutions.

Passionfruit are shallow-rooted, so avoid cultivating directly underneath the vines. Keep grass under the vines mown short – it isn’t advisable to use herbicides and you can protect the base of the vine with a collar of corrugated plastic drainage pipe to avoid inadvertent stem damage from overzealous mower or weed-eater operators. You can mulch under the vines to help with moisture retention, weed suppression and add some extra nutrients (perhaps fostering healthy soil flora and fauna at the same time), but be careful to avoid piling mulch right up against the stem itself, as this can lead to collar rots.

Pruning

To form an initial framework, choose some strong shoots and train them up your trellis or support structure, forming laterals. Aim to space these about 40 cm apart. Fruiting growth will arise from these laterals – cut each of these pieces back to two buds once fruiting ceases, removing any dead, diseased or unwanted growth at the same time. Aim to replace the main laterals/leaders one by one after three or so growing seasons to keep the vine productive.

In warm climates with mild winters, passionfruit vines can be pruned after harvest, but in cooler, frost-prone climates, leave it until spring when the danger of frosts has passed (in general, the latter option is best for the New Zealand climate). In the former situation, you can be tough when fruiting is finished and prune passionfruit vines hard to remove all dead wood – commercially, not a lot is left. Frosted vines cut right back will usually sprout again from the base in spring.

Pests, diseases and what to do about them

Passionfruit are very susceptible to soil-borne diseases, so when replanting, you should remove the old or dead plants with a significant quantity of soil around their roots. Diseases affecting passionfruit are mainly fungal, (e.g. passionfruit brown spot, Alternaria passiflorae) or bacterial (e.g. passionfruit grease spot, caused by Pseudomonas passiflorae) and are treated with copper sprays, e.g. Yates Liquid Copper applied at seven to ten day intervals, paying particular attention when conditions are wet.

The passionvine hopper, Scolypopa australis is a namesake insect pest of passionfruit, sucking the sap and leaving sticky deposits of honeydew which make the plant susceptible to sooty mould. They can be combatted with applications of Yates Nature’s Way pyrethrum or Organic Citrus, Vegie and Ornamental spray - apply in the evening for best effects.

Varieties: My top picks

Incredible Edibles stocks P. edulis (purple or black passionfruit) ‘Black Beauty’ and the yellow variant P. edulis var. flavicarpa ‘Golden Passion’.

As an alternative to the noxious banana passionfruit, Incredible Edibles also provide the attractive red-flowered vanilla passionfruit, Passiflora antioquiensis, purported to have the most superior flavour of all the passionfruit species. It is a close relative of banana passionfruit but much less vigorous in its growth habit.

What to do with your crop

The tangy, aromatic, juicy flesh of passionfruit with its unmistakeable crunchy seeds lends a familiar flavour hit to many popular desserts from pavlova to cheesecake. A component of many fancy cocktails and fruit punches, a few passionfruit scraped into a fruit salad provides an instant lift, and the beauty of these little flavour-grenades is that they lend themselves well to various methods of preservation without any loss of flavour.

If you find yourself with a glut of passionfruit, you can simply scoop the pulp and freeze it in ice-cube trays, with or without the addition of sugar, popping out and free-flow bagging the cubes when solid. You can preserve the pulp in heavy syrup (1 cup sugar to every cup of passionfruit pulp) and bottle it via the overflow method if you prefer a shelf-stable storage option. See Your Backyard Fruit Bowl: Apricots for a detailed bottling method.

I like to make passionfruit curd as a filling for cakes and for stirring into plain yoghurt to brighten cold winter days. I use Nigel Slater’s recipe: https://www.theguardian.com/lifeandstyle/2010/mar/07/nigel-slater-lemon-curd-recipes and use four whole eggs, decrease the quantity of lemons from four to two and add ½ cup of passionfruit pulp in their place. Limes are a nice substitute for lemons in this combination if you have them. I pack the finished curd into clean plastic containers holding about 200-250 g (recycled hummus or sour cream tubs work well here) and stow them in the deep freeze for up to a year (if it lasts that long!). Thaw the curd in the fridge overnight, give it a quick stir, and it’s just as the day you made it. Make sure you use the thawed curd within five days and keep it refrigerated.

A few years ago I made some tasty passionfruit melting moment biscuits using a recipe by Wellington food writer Lucy Corry, which was itself adapted from a recipe by New Zealand culinary stalwart Tui Flower. They were delicious, and interesting in that passionfruit pulp was incorporated into the biscuit dough as well as the filling. Highly recommended, and you can find the recipe here: https://www.stuff.co.nz/life-style/food-wine/68488286/three-ways-with-passionfruit

Historical context – genus Passiflora (passion flowers or passion vines)

Source: https://en.wikipedia.org/wiki/Passiflora

The name of this genus can be traced back to Spanish missionaries in Brazil in the early 1700s, with the etymology referring to the passion of Jesus in Christian theology. The unique physical structures and numbers of each flower part on vines in this genus were adopted as symbols of the last days of Jesus, and especially of his crucifixion.

The pointed tips of the leaves were taken to represent the Holy Lance.
The tendrils represent the whips used in the flagellation of Christ.
The ten petals and sepals represent the ten faithful apostles (excluding St. Peter, the denier and Judas Iscariot, the betrayer).
The flower's radial filaments, which can number more than a hundred and vary from flower to flower, represent the crown of thorns.
The chalice-shaped ovary with its receptacle represents a hammer or the Holy Grail.
The three stigmas represent the three nails and the five anthers below them the five wounds (four by the nails and one by the lance).
The blue and white colours of many species' flowers represent heaven and purity.


Anna-Marie Barnes is an active member of the New Zealand Tree Crops Association who endeavours to grow and preserve as much of her own fresh produce as possible. When the weather’s no good for gardening, she can usually be found inside working on a batch of homemade cheese or soap.

The New Zealand Tree Crops Association is a voluntary organisation promoting interest in useful trees, such as those producing fruit, nuts, timber, fuel, wood, stock fodder, bee forage and other productive crops. Find out more about the NZTCA here: https://treecrops.org.nz/
Disclaimer: the information supplied above is of a general nature and provided as reference material only. In regards to pest and disease control, please consult your agrichemical consultant for suitable products, application rates and further region-specific information.

Image credits
Passionfruit - Image by Christiane from pixabay.com
Passionfruit flowers and foliage - Image by Isabel Chen from pixabay.com
Bowl of passionfruit - Image by Lynn Greyling from pixabay.com