If there was one fruiting plant that people loved to grow but complained about most frequently, it would have to be the humble passionfruit. Over the years I worked at 6PR and took talk back radio calls from people, I would have answered the same few questions hundreds of times. Why does my passionfruit vine grow strongly but doesn’t fruit? Why are my passionfruit flowers different to normal passionfruit flowers and the fruit tiny? Why am I only getting fruit in winter and why don’t my fruit ripen? The answer to the majority of questions gets down to three essential elements; the variety you select, the weather conditions and bee activity during flowering.
Passionfruit are one of the easiest climbing plants to grow and they do super well in sandy soils. The most commonly available forms of passionfruit are the black pasionfruit varieties, Passiflora edulis. There’s a wide array of varieties around these days, with some sold grafted onto a rootstock and others as seedlings. The reason for grafting is to prevent fusarium wilt, a disease that affects many of the tropical varieties when they are grown in heavy soils that waterlog in cold weather. Areas with sandy soils are less at risk, so grafting is not as important.
The most common problems
Lack of fruit set is the biggest complaint. Passionfruit tend to flower twice a year and have the potential to produce two good crops. The primary reason for failure to fruit in the spring and summer gets down to pollination. There are two main reasons for this. One is bee activity. Having companion plants that flower at the same time as your passionfruit to attract large numbers of bees is a good way to solve this problem. Roses planted near a vine, artichokes allowed to go to flower and Grevilleas are all good companions. Poor pollination of flowers is prevalent with some varieties more than others and my experience is that ‘Panama Red’, ‘Panama Gold’ and the Nellie Kelly black passionfruits are more prone to producing one crop a year that often arrives in winter.
The other issue with lack of fruit set is a little harder to control. Humidity must be high for passionfruit to succeed in many areas. To assist with this, apply a light mist of water over your plant’s foliage and flowers in the morning whilst in flower. A thick pith and little pulp or malformed fruit is another common complaint. This again this relates to pollination and humidity issues.
A common problem of winter fruit crops is the fruit not turning purple or ripening. Passionfruit matures and is ripened by lots of sunlight and heat, so winter crops tend to hang for months before falling off the tree. Leave the fruit to drop before eating it as it’s going to be the sweetest it can be then. It will always be more tart in flavour if it’s not exposed to sunlight, so make sure you choose the year-round sunniest spots in the garden to plant them.
The last problem is something you need to consider when you decide which variety of passionfruit to grow. A lot of people report their black passionfruit doesn’t produce fruit or, if it does, they are small yellow fruit and the flowers are not purple but instead blue. The foliage is a different shape and the plant suckers with shoots popping up everywhere. This is the rootstock suckering or producing growth from below the graft point. Passionfruit growers graft black passionfruit varieties onto a rootstock species known as Passiflora caerula, the blue-flowering passionfruit. This rootstock is vigorous and resistant to fungal diseases, which are vitally important for passionfruit grown in heavy soils.
However, Passiflora caerula is a weed with no value in sandy soils and has potential to become invasive across your garden. It will take over and the original black passionfruit will be smothered out as it is not as vigorous as the rootstock. It needs to be eradicated, with best results coming from using a systemic herbicide. With this in mind, my advice is to buy passionfruit that are not grafted if you can get away with it. If you do buy a grafted variety, it’s important to watch carefully over the first 12 – 18 months to ensure no suckers emerge from under the graft union. If they do emerge as new shoots, remove them by pulling them away from the stem (don’t cut them with secateurs).
The key to growing passionfruit successfully is the location you put them in, as they love a sunny spot. A typical black passionfruit vine will produce 400 fruit a year in the third year of its development if it’s in good quality soil and an optimal position.
Feeding passionfruit with fruit-promoting fertilisers once mature is vitally important. These high potassium fertilisers promote more flowering, better pollination and a sweeter fruit taste. Applying a controlled-release product is best. Avoid high nitrogen fertilisers such as cow and chicken manure once your passionfruit is developed. They promote lots of growth but can contribute to the fruit having lots of pith and little pulp.
It’s important to water consistently, but two drinks a week is enough for a mature established vine. It’s also important to water the plant at the same frequency and volume when it’s in flower as when in fruit. A lot of people water fruiting plants more heavily when fruit appears, but this can cause problems with the quality of produce.
The best time to prune passionfruit is when the fruit has fallen. Thinning your passionfruit vine is a good idea, as this encourages lots of new fresh growth that will supply the flowers for your next crop. Often pruning can trigger new flushes of flowering. It’s always better to lightly prune regularly than more severely only occasionally.
Ten of the best black passionfruit varieties
Black passionfruit varieties found commonly in garden centres include;
- Nellie Kelly grafted black passionfruit.
- ‘Panama Red’ and ‘Panama Gold’, both red and gold panama come as seedlings or grafted under the Nellie Kelly brand.
- ‘Sunnypash’ black grafted passionfruit.
There are also new forms of black passionfruit have been released in recent years, including;
- ‘Tutti Fruiti’, a variety prone to diseases but fruits four times a year and tastes marvelous.
- ‘Sunshine Special’, sold as grafted or seedlings.
- ‘Norfolk Island’, a winter-ripening passionfruit with a more sour taste.
- ‘Big Boppa’, a larger fruiting form.
- ‘Pink Cheeks’ has a pink blush on the skin of the fruit and sweet flavour.
- Passionfruit supersweet 96A, a new pink-skinned passionfruit that is a heavy summer cropper and comes grafted for disease resistance.
- ‘Sweetheart’, probably the most sought-after eating variety of the black passionfruit because it’s so sweet and easy to eat.
Five exotic species worth collecting
The passionfruit family consists of some 500 different species, with a few hundred varieties of the black form. There are some unique passionfruit worth collecting if you are keen to try something different.
- Banana passionfruit is not only delicious, but an amazing plant with huge pink blooms that are unlike the common passionfruit flower we are familiar with. The fruit is yellow and oblong and tastes simply delicious, although is a little more tart than black passionfruit.
- Sweet lilikoi (Passiflora edulis var. flavicarpa) is an improved form of the golden passionfruit and a natural variation of a black passionfruit originating in Hawaii. It is a truly delicious variety that delivers fruit in late summer.
- Passiflora laurifolia, commonly known as the water lemon, is a sweet passionfruit with a mild lemony flavour and strong lemon-passionfruit aroma. It’s a tropical plant so needs protection from frost but once established grows strongly during summer.
- Sweet granadilla (P. ligularis) is generally thought to be the finest passionfruit of all. It has purple and white flowers and large orange fruits filled with exceptionally sweet and fragrant pulp. It is frost sensitive, so needs a warmer area to thrive.
- Giant granadilla (P. quadrangularis) has crimson flowers and melon-sized fruits that have fragrant, sweet pink pulp. The flowers need hand pollination to fruit to their best potential and it also requires a warmer climate.
About the Author – Trevor Cochrane
Trevor is a born-and-bred proud West Australian who grew up on a dairy farm in Mundijong, just outside of Perth, WA. He launched the media company Guru Productions in 2002 that has since produced over 750 episodes of television telecast on Channel 9 nationally and is now seen in over 100 countries across the globe in 14 different languages. In the years since creating The Garden Gurus he has created and produced over 50 hours of international travel shows, food and wine programs, local WA food program Our State on a Plate and the Destination WA travel series. All Guru Productions projects appear on Channel 9 and WIN Television, as well as nationally on the popular digital TV channel 9 Life. Trevor’s passion for gardening has seen him write four books and regular columns for the The Sunday Times and The West Australian Newspaper.