Now I don’t want to gloat, but here it is winter and we’ve been enjoying delicious, homegrown passionfruit for months. Which is just as well for my vine’s survival, as we didn’t see any crop at all last summer. Spring and most of summer went by with lots of growth but few flowers. It was if you recall a cool, grey summer along the east coast, but towards the end of summer the vine gave up sulking and burst into flower. By the first days of autumn it was bedecked with green fruit.
The fruit hasn’t ripened all at once but gradually giving me a steady supply to eat fresh with a spoon or as a topping for yogurt or fruit salad. Now the chooks are back in production I should lash out and make a pav, which is surely the traditional place to use passionfruit.
Passionfruit is an interesting plant but not without its problems. It is one of Australia’s favourite backyard crops but I’d venture to say it brings more questions to talkback garden shows than even lemons do.
The main concerns revolve around fruit (or I should say lack of it) but gardeners are also concerned about when to prune it and how to feed it. More recently suckers are showing up as a problem too.
Pests – from passionvine hoppers to rats – also raise concerns. There have even been questions asked about passionfruit on this site.
After many years of both growing passionfruit and also advising others, I’ve decided that to grow a strong, productive passionfruit vine is part good gardening and part dumb luck.
They also need full sun, good drainage and shelter from the cold. Fertilise vines with pelletised chicken manure or citrus food, spreading fertiliser along the root system. Water well particularly after planting, while times are dry and when plants are flowering and crops are maturing.
Nellie Kelly, a large-fruited black passionfruit, is the most popular homegrown variety and the one I am growing, but others you’ll come across at the nursery are Panama Red, Panama Gold and Pandora. These last three do best in warm or at least coastal climates. I wouldn’t expect any of them to fruit here in Kurrajong.
Another bone of contention with passionfruit seems to be whether or not they need a ‘friend’. Some Panama varieties for instance fruit better with cross-pollination (that is two vines) but Panama Gold Select is self-fertile. Nellie Kelly is also self-fertile.
Popular in days gone by was the banana passionfruit (Passiflora mollissima), but it is now considered a weed. This species was popular as, not only easy to grow and it grew on its own roots, but was it is self-fertile and produced lots of elongated yellow banana-shaped fruit.
For decorative rather than fruiting passionfruit there is the beautiful scarlet passionflower, Passiflora coccinea, also known as red granadilla and for cold climates there are ornamental forms of the blue passionfruit, but I’ve not seen these growing in Australian gardens.
Passionfruit though are basically are warm climate plants. Tropical, subtropical and warm coastal zones grow the best passionfruit although there is a passionfruit farm just up the road from us in Kurrajong Heights – or at least there was one. The passionfruit flourished in what is a frost-free microclimate with fertile soil.
Cold conditions and wet soils can lead to poor growth, death of the vine or poor fruiting so always plant passionfruit in a warm, sunny, sheltered spot with free-draining soils. Passionfruit need lots of space for their root systems so don’t grow them in pots.
In tropical and subtropical climates, passionfruit vines fruit within six months of planting. In these climates spring-planted vines may be fruiting by late summer and fruit production continues through winter.
In temperate zones vines however can take 18 months to reach maturity – so that’s a year and half before you can expect them to begin flowering and fruiting. That’s a long wait! Indeed, a spring-planted vine may not flower and fruit until its second summer so that’s quite a long time when plants may only survive for five years before they are hit by virus disease and die.
But a lack of fruit isn’t always just due to immaturity. Lack of regular water, lack of pollinators or even sudden cold winds can all take their toll on fruit. Too much shade can also slow ripening and this is where pruning can be effective. In late winter or early spring carefully remove some of the tangle of stems so that fruit and flowers when they appear are better exposed to the light.
Fruit that falls from the vine but isn’t black may be ripe (so always check) but it can also be dropped if the weather suddenly turns cold or the plant lacks water. Pest insects such as passionvine hopper feeding on the vine can also lead to fruit drop. Watch out for these insects while they are young. They appear as ‘fluffy bums’ – that’s the name given to the cute-looking nymphs. They are easier to deter with a jet of water or control with a chemical spray as juveniles than as adults (which resemble lacy-winged moths).
But getting back to passionfruit. Fruit colour at ripening can be variable. Usually green fruit ripens to purple or black but some ripe fruit may not be highly coloured. If green fruit drops to the ground it is always worth tasting it to see if it is ripe, despite it not being highly coloured. Ripe fruit left on the ground may get sun burnt so regularly collect fruit. Also keep the ground around your passionfruit clear of weeds or long grass so it’s easier to find fallen fruit.
Fruit that forms but contains little pulp may have been poorly pollinated, but again there can be other things going on such as stress due to insect pests, cold or lack of regular water.
Lots of flowers but no fruit may be due to poor pollination. If the weather is cool, wet, windy or even overcast during flowering, pollination and fruit set may be poor. A lack of pollinating insects (often made worse by bad or cloudy weather) can also affect cropping. Hand pollination (using a dry paintbrush to transfer pollen to the female part of flowers) can overcome some pollinating problems and is most successful done early in the morning.
Encourage bees and other pollinating insects to vines by planting herbs such as borage.
My biggest beef with passionfruit however is suckering. Most passionfruit are grown as grafted plants to overcome problems with fusarium wilt and other soil-borne fungal diseases. Home garden plants are usually grafted on to blue passionfruit (Passiflora caerulea).
Blue passionfruit is a vigorous plant that may sucker particularly where there is root disturbance or if the grafted part (the scion) dies. It produces inedible yellow fruit, but this fruit also helps it to spread.
Watch for suckers (look for the distinctive five fingered, blue-green leaf as well as its blue flower) and remove suckers or seedlings promptly. If a vine dies carefully dig up the root system to avoid future problems.
There are other rootstocks and I do wish they were used more for home garden varieties. Commercial vines are usually grafted on to Passiflora edulis f. flavicarpa, a rootstock developed in Queensland that is disease resistant and not prone to suckering.
Some varieties are also grown from seed or cutting to overcome suckering problems. Panama Red and Pandora may be sold as seed grown plants which means they are growing on their own roots.
Passionfruit make excellent screening plants and add a lush leafy tropical feel to the garden. But, if you plant one, remember that they’re not always going to be trouble free, but most come good and produce truly delicious fruit. Speaking of which, I’ve just collected eight eggs from the chooks and a dozen fruit from the passionfruit so I am about to whisk up that pavlova to celebrate.
[Like to know more? Here's another post on Growing Passionfruit by Marianne Cannon]