Raising vines from seed is the most cost-effective way to establish commercial plantings. Choose a heavy cropping plant and collect average sized fruit in February or March. Make sure the fruit is blemish-free, but carry out taste testing too.
Scoop out the pulp and place in a glass container with 60ml of commercial hydrochloric acid. Stir every half hour for three hours. Use a funnel to pour the pulp into a large bottle filled with water. Cap and shake well to separate the seeds from the pulp. Repeat the washing process until the seeds are clean, then strain in a fine mesh sieve. Dry the seeds in a thin layer on paper towels in a cool, dark cupboard.
Allowing for germination and propagation losses, you will need about 100g of dry seeds to raise 200 plants. Sow as soon as possible in seed trays. Grow on in individual pots in a heated glasshouse over winter, before planting out in October. Seed can also be sown outdoors in spring.
Pruning
Pruning is essential to maintain productivity as vines bear fruit on the current season?s growth. If you don?t prune, you?ll end up with a snarl-up of stems.
From the second season, prune annually, almost back to the main leader. Always wait until the vines are growing well - October is an ideal month to start the job.
Manipulating pruning times to benefit from high early and end of season prices is a tricky juggling act. Prune too soon and an unexpected cold snap could cause severe dieback. Prune too late and you?re also at the mercy of the weather, the fruit could fail to colour up satisfactorily before the temperature drops.
Pest problems
Fungal diseases can devastate commercial plantings and regular copper sprays are necessary. Apply copper once a month during winter, and every 10-14 days during the peak growing season. Brown spot shows up as muddy splotches on leaves and fruit and is prevalent in spring and early summer. Grease spot attacks leaves, stems and fruit, causing khaki-green oily marks, often surrounded by a pale yellow ring like a grease stain. It can cause premature fruit drop, defoliation and stem lesions.
Crown canker is a serious fungal infection with no real cure. It infiltrates weak spots in the stem which may have been caused by frosts, slug or snail damage, growth cracks or splits. Plants wilt quickly and die. Infected plants must be dug up and burnt.
Another nasty piece of work is the woodiness virus, which causes yellow-spotted, crinkly, mottled foliage and scabby fruit. It comes on late in the season and spreads from plant to plant like juicy gossip. Left unchecked, woodiness will destroy a passionfruit orchard. Remove infected vines immediately.
Root rot caused by Phytophthora can also be a problem. Try to prevent it by planting in well-prepared, free-draining soil.
As for insect pests, watch out for passionvine hoppers, green vegetable bugs and thrips. "In hot, dry weather, thrips can ruin your fruit for export unless you get rid of them quickly," Tony Dimmock warns. Passionvine hoppers suck sap from stems and ooze sticky honeydew, which can lead to sooty mould problems.
Spray insect pests with Nuvos - the only insecticide approved for use on commercial passionfruit.
Picking and Packing
Expect your first small crop after 18 months, followed by heavy yields (up to 12 tonnes per hectare) for the next two seasons. Production will begin to drop away by year five.
When ripe, the purple fruit will fall to the ground. It is not advisable to pluck fruit from the vine. Collect fallen fruit as early as possible in the morning and again later in the day, to prevent sunburn blisters.
Each fruit must be wiped cleaned to remove any copper residue before being packed. Handle with care so as not to scratch the skin.
Reprinted from "Growing Today" October 2001
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