Trellis Construction
Horizontal trellises have cross-pieces at the top of each post with 2-4 wires strung horizontally 60 cm (2 ft.) apart along the top of each cross-piece. Vertical trellises consist of heavy posts without cross-pieces, with 2 or 3 wires strung along the row like barbed wire fencing, attached to the posts from the top down at intervals about 30-40 cm (12-16 in.) apart.
Trellis wires should be No. 9 or 10 galvanized steel. The posts need to be stout enough to withstand the weight of the vines throughout a season that normally includes the buffeting of strong winds. Ideally they should be long enough to provide a trellis height of 1.5 m (5 ft.), with 45-75 cm (18-30 in.) in the ground. Trellis rows should be oriented north-south for maximum exposure to sunlight, and the vines should be allowed to grow together along the trellises to promote cross-pollination.
Trellises are required for the commercial production of passionfruit. Trellises contribute most to the cost of production of the crop and should be constructed properly. Trellises should be constructed in the same direction with the wind wherever possible. On sloping terrain, trellises should be constructed across the slope. Although the passionfruit has been shown to be more productive if allowed to climb a tall tree, trellising is recommended for many reasons.
Large crops are obtained on trellises 7’—8’ tall or taller. Such a tall trellis with a wire attached near the top of the posts and two other wires each attached near the ends of cross-bars a foot or more below the top of the posts tends to give the best spread of vines and the greatest convenience of working in the planting but is expensive especially for a short-lived planting.
In rocky or gulch areas it is often possible to use standing trees to guy the trellis wires. In some circumstances heavy cables are stretched between trees to support lighter wires at right angles to the cable. In other locations, rather tall trees have been used and the wires guyed to shorter trees or posts, giving a tent-like appearance. However, a standard trellis has the advantage of giving early returns, greater yield, accessibility for fertilization and harvesting; also more leaf surface can be exposed to the light.
In constructing the standard trellis, it is desirable to use at least eight or nine gauge heavy wire. To withstand the weight of the vine and tension on the wire, the wire should be placed on top of the cross-arm or post and stapled securely or holes drilled through the cross-arm and post and the wire strung through the holes. It is then possible to adjust the tension of the wires which is not possible when wires are stapled.
If a wide spacing of 20’ or more is used between posts, the cross-arms must be mortised into and securely nailed or bolted to the post. Greatest strength and stability, with very little loss of surface, are attained when the wires are tied directly to the end post, rather than securing the wires to a cross-arm on the end or strainer post.
With the yoke trellis, the cross-member at the end of the trellis should be sufficiently sturdy to support the strain that will be placed on it. A 20’ length of trellis 3’ wide is required to support a minimum weight of 150kg of vine and fruit.
The posts should be about 10’ long, the end posts at least 3’ in the ground and firmly braced to support wire tension and vine weight. Inside posts need not be planted so deeply.
A vine offers considerable wind resistance after having become established on a trellis so this must be securely constructed to prevent both vine and trellis from being blown over by a strong wind.
Posts may be almost any material adequate for supplying strength for five or more years and may be 10" butts for anchor posts, 6" butts for internal posts and 2" x 4" or more for cross-arms.
All wooden posts must be treated to prevent decay, especially the portions in contact with soil. Creosote, which is toxic to plants, should not be used. Copper naphthenate may be brushed onto the wood in two applications about 30-40 minutes apart, then the wood permitted to dry completely.
Transplanting and Training
Root-pruning should precede transplanting of seedlings by 2 weeks. Transplanting is best done on a cool, overcast day. Plants are transplanted during the cooler part of the day (early morning or late evening).The soil should be prepared and enriched organically a month in advance if possible. Grafted vines must be planted with the union well above ground, not covered by soil or mulch, otherwise the disease resistance will be lost. Mounding of the rows greatly facilitates fruit collection.
Plant passion fruit vines in full sun except in very hot areas where partial shade is preferable. One or two vigorous leaders are selected and trained to the top wire. The vine can be rather rampant, so it is important to plant it next to a chain link fence or install a strong trellis before planting. The plants can also be trained into an attractive arbor.
Plants in fertile soil extend their stems about 3 m per year. Each year during the annual dry season, the leaves fall off and the twigs die, leaving the main stem and a few important branches alive to rebuild the crown after the rains begin. Because fruiting takes place on new wood, light pruning does not reduce yield. Plants live from 3 to 8 years and do not resprout. Commercial stands are managed in vineyards, somewhat like grapes. They are planted in trellised rows 4.5-6 m apart and spaced 3-4.5 m apart within rows. The orchards are replanted every 4 to 6 years. Alternately, vineyards may be established using small trees or bamboo as standards. Fruiting plants can even be grown in pots under glass. The roots normally form mycorrhizal associations and benefit from inoculation with superior strains of fungi.
Some kind of temporary support at each plant is necessary to train it to get a good hold on the wires of the trellis, after which it takes care of itself and needs no other support. The principal objective is to get the vine to the trellis wires in the simplest, quickest and least expensive manner.
If the young vine is supported in an upright position, with a strong wire or light pole to grasp, it usually will grow quickly to the trellis wire with a minimum of lateral branching. A terminal branched portion of bamboo, inverted and hung over the trellis wire, provides an excellent support for the vine and eliminates the necessity for frequent tying.
Four to six laterals may be trained in both directions onto the overhead wire, and the sooner they come to a horizontal position on the trellis the more quickly they will flower and fruit.
Passion vines in their native state clamber up available trees or rocks and spread out to catch the available sunlight. The yellow passion fruit has naturalized in this manner. In cultivation, vines should be trained to cover the wires of the trellis or fence on which they are grown.
Young vines are trained by aiming a growing up toward the top of the trellis and once there, allowing a shoot to grow along each wire in each direction. A 2-wire trellis provides 4 sprouts growing along the trellis away from the vine's trunk. Once started, the vine should be allowed to grow without pruning throughout the season, since the more vine there is, the more bearing surface there will be. With self-incompatible forms of yellow passion fruit it is particularly desirable to allow 2 different, cross-fertile vines to grow through each other and intertwine so as to promote heavy fruit production.