Be warned! Grafted passionfruit are a ticking time bomb in your garden, particularly in temperate areas. My coastal friends had a splendid grafted specimen, Nellie Kelly, which produced excellent crops for the first few years. Trouble started when they set off on an expedition to Tasmania. Returning home in spring, they discovered that all hell had broken loose in their garden! Nellie Kelly’s rootstock had gone berserk, throwing out hundreds of suckers up to 10 metres away from the main stem, and fruiting had stopped.
The culprit in all its beauty
The rootstock used for grafted passionfruits is from an exceptionally vigorous and invasive passionfruit variety from South America called Passiflora caerulea. Fortunately my friends took a break from gnashing their teeth and tearing their hair, to take some mug shots of the culprit, which are, you will agree, fascinating and beautiful.
P. caerulea is used as a rootstock because it is extremely robust, cold-hardy and disease resistant. The down side is that it readily sends sub-surface runners and shoots out which require constant vigilance and removal. Left unchecked, the rootstock overwhelms the top of the graft which is where the desired variety you’ve purchased, actually grows from. It can eventually take over your entire garden. And it’s not the only Passiflora to have these qualities.
Another offender, Passiflora edulis – has the distinction of being on the Global Invasive Species Database.
In temperate climates this rootstock smothers vegetation in yard and bush, so it’s an environmental disaster as well as a horticultural one! It also produces natural cyanide in its stems, leaves and immature fruits, making it dangerous to any animals that eat it. The Royal Horticultural Society considers P. caerulea “somewhat poisonous” to both humans and pets. In particular, dogs should be protected from contact with this plant, especially any that have a history of snacking on foliage.
It’s less of a problem in areas where the winters are cold, but still requires constant monitoring and control.
If you live in a warm-temperate, subtropical or tropical zone, the good news is that you’ll be able to grow non-grafted Passionfruit quite easily and with much less maintenance.
So what to do if you’re already in the grip of a Passionfruit rootstock invasion? Online advice abounds, generally favouring chemical elimination methods. There’s also the more environmentally benign Bradley Method. All methods involve a lot of hard work. Here’s some information that may assist you.
The culprit- detail.
Method 1- the Bradley Method for Control of Invasive Plants, first developed in Australia by the late Joan Bradley and her sister Eileen. There are many references to this sustainable technique, online. Here’s one example: http://courses.washington.edu/ehuf462/462_mats/bradley_method.pdf.
Method 2- Scrape sections of the vine down to the white fibrous layer and immediately paint the exposed area with concentrated herbicide (eg: glyphosate). Repeat the process as high up the stem as can be reached, and where possible, scrape both sides of the stem. This should be done on ALL stems.
Method 3- the Scorched Earth Policy – keep poisoning (spraying with glyphosate) and weeding (including pulling up underground runners) until there is not a skerrick coming up anymore.
Whichever method you choose, you will need to keep a watchful eye out for at least a few years to catch any undetected suckers.
The history of the name “Passiflora” is fascinating.
The genus was originally was named “Espina de Cristo” (Christ’s thorns) by Spanish Christian missionaries in South America. They saw each part of the complex and intricate flower as symbolising the crucifixion story – the Passion of the Christ. Five sepals and five petals refer to the ten faithful apostles (excluding St. Peter the denier and Judas Iscariot the betrayer). Three stigma represent the three nails that held Christ to the cross, while five anthers represent his five sacred wounds.
Image from http://passionflowerpower.com/sacred-symbolism.php
The tendrils of the flower are said to resemble the whips used in the flagellation, while the dozens of filaments depict the crown of thorns. The blue and white colours of the flowers represent Heaven and Purity.
The Passion Flower can be found in stained glass window designs in Christian churches.
Older Germanic names include Christus-Krone (“Christ’s crown”), Christus-Strauss (“Christ’s bouquet”), Dorn-Krone (“crown of thorns”), Jesus-Lijden (“Jesus’ passion”), Marter (“passion”) or Muttergottes-Stern (“Mother of God’s star”).
The blue Passion Flower is also sacred in India, called “Krishnakamala” in Karnataka and Maharashtra, and “Paanch Paandav” in Uttar Pradesh and the north. The five anthers are interpreted as the five Pandavas in the Hindu epic, the Mahabharata, with the Divine Krishna at the centre, opposed by the army of one hundred at the outside edges. The blue of the flower is said to be associated with the colour of Krishna’s aura.
There’s plenty of information online. Just search under “invasive rootstock” and this perpetually escaping felon will appear as the top search results. Many people call for a banning of P. cearulea rootstock.
Let me know if you’ve tried any of the 3 methods for eliminating this pest.
Do you grow Passionfruit in the Mudgee region? I’d like to know which variety you have.
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