Vines should be pruned in late winter when they are not actively growing. All dead and weak wood should be cut out and the vine pruned back to vigorous, well-budded stems so that it can resume healthy, active growth in early spring. Disinfect pruning shears between each pruning to avoid spreading disease from vine to vine. A good time to make the first fertilizer application is after pruning.
The pruning of passionfruit vines is conducted in order to reduce the level of pests and diseases and to encourage new vine growth. Heavy pruning should only be performed once per year, after the July to September crop. Since pruning tools are means by which diseases are spread they should therefore be kept clean.
Generally, pruning is done while the vine is dormant and consists of removing any growth that is weak or trailing on the ground, and shortening strong canes by about one-third. Regular pruning is necessary because the fruit is borne on new shoots arising from old canes. This pruning encourages new growth and removes unproductive wood.
A spur should be left at the base of each cane to replace the old cane after it has borne fruit for a year or two. This pruning is done when the vine begins active spring growth. Vigorous vines branch freely and branches that trail on the ground should be removed.
Severed stems and pruned branches should be allowed to become dry and brittle so that they can be disentangled easily from the vine.
In Australia and New Zealand, purple passionfruit vines in commercial plantings usually are pruned to facilitate spraying or to force new growth.
In South Africa, they are pruned to maintain an environment which discourages infestation and encourages healthy growth, and to facilitate cultural practices. However, unpruned vines of purple and yellow passionfruit have been shown to consistently out-yield those which have been pruned.
The evidence on pruning is conflicting. Although in the literature there are frequent admonitions against severe pruning, some growers do practice severe pruning of established vines in spring, cutting each shoot of the preceding year back to a stub with 2-4 or 5 buds to start all new shoots close to the wires. Others merely cut out the shoots that trail to the ground and thin out shoots where they become thick enough to lodge abscissed mature fruit. This method is better suited to plantings where the fruit is permitted to fall for harvest.
In Sri Lanka, pruning all shoots to stubs with two or three nodes in the fall months of January or February, soon after the crop was off, was reported to cause heavier yield than any less severe pruning or no pruning at all.
On the other hand, in some experiments in South Africa, certain types of pruning seemed to reduce yield. Possibly in Sri Lanka, where fruit-setting tends not to be very good, the severe pruning caused some of the shoot growth and flowering to be in seasons more favorable for setting.
In Hawaii, it has not been determined whether or not the commercial yellow passionfruit requires periodic pruning. For short-lived plants trellising and pruning are expensive, as is the rather long harvesting period with rather frequent gathering of fallen fruit.
