The Naranjilla, botanically known as Solanum quitoense, belongs to the same family as the potato, tomato and tamarillo. It is one of those exotic fruits one hears about but rarely encounter in this country.
To those who know this fruit, they are generally well-liked, although a first encounter with the fruit may lead to disappointment, as the fruit tends to be very acid or almost bitter when eaten before maturity.
Like so many 'new' exotic fruits, the Naranjilla is native to the mountainous regions of Ecuador and Colombia in South America. Wild forms of the Naranjilla are found in mountain forests from 1200 to 2000m altitude in the Andes. The plant itself can be immediately recognised by its spectacular large, velvety, purple-veined leaves.
The plant is multistemmed, the stems being pale green and spiny and reaching a height of about 2m. The round, orange, golfball-sized fruits are carried on short stalks on the stem. The green unripe fruits are covered in dense fine hair which rubs off easily when the fruit matures. The Naranjilla plant is a perennial, usually lasting about five years under favourable conditions.
Naranjilla is a Spanish word meaning 'little orange'. The fruit does somewhat resemble an orange in shape and colour, but there the resemblance stops. The skin is thin but leathery. The juicy pulp has the consistency of tomato pulp, moss-green in colour, embedded with flaky seeds.
Our experience is to wait to harvest the fruit until they fall off, usually between the months of October to December. Often the fruit splits open when they ripen. At this stage the fruit is in optimum condition for consumption. The colouration of the fruit from green to yellow-orange takes place several months before maturity. During this stage, the fruit is too immature to eat, although by appearance alone one would be tempted to eat it.
The fruit of the Naranjilla is most popular in Ecuador where it is used widely - commonly made into juice, used in sorbets, and made into ice cream. The juice may be diluted and sugar added to make a very refreshing drink of unique flavour. Although not commercially exploited on a large scale, Naranjilla can be bought at most market places in South American towns and cities.
The Naranjilla has been tried in many countries of the world without a great deal of success. The plant has exacting climate requirements. It does not tolerate frosts nor temperatures above 28°C. It prefers humid constant temperatures between 10 to 25°C throughout the year. These conditions are hard to find, and New Zealand can only partly satisfy these requirements.
Our winters are too cool for the Naranjilla, yet the plant survives our climate. During the winter months the plant is set back, losing most of its leaves. Greatest tree losses occur during the cold months as root rot diseases and various stem rots take their toll. Surviving plants are either genetically stronger or a superior microclimate helps in their survival through winter.
The Naranjilla was first introduced in this country in 1956 by Dr. Harold Mouat of DSIR. Plants were grown at the Mount Albert Research centre and some were sent to Kerikeri orchardists. Nothing has ever been reported about what became of these trees.
The writer introduced some Naranjilla seeds in 1968 from Costa Rica. These plants produced fruit and continued to survive for about three years, with the exception of one plant which has survived to this day. The longevity of the latter is probably due to its growing site, semi-shade under an old Puriri tree. Subsequently seeds have been imported by different people over a number of years. No one seems to have yet tackled commercial production of the fruit.
The seed can be extracted from the fruit and sown straight away. Seedlings emerge in about a month and can be pricked out when large enough to handle. The plants are difficult to handle in pots or containers, as they are very water-demanding. Young plants may be lined out in the field when quite small, during the late spring.
Growth is rapid. Under favourable conditions, flowers and fruitset occurs about six months from planting out. Spacing in the field would need to be 1.8m each way.
Interplanting with leguminous crops such as beans, alfalfa or the like helps to maintain the ground cover and mulch which the plant requires.
The main problem of growing Naranjilla is the susceptibility of the plant to numerous diseases and pests, in particular, Phytophthora root rot and nematode insects in the roots. Both of these limit the life of the plant.
A well-drained soil does help, but is no answer in itself. Stem rots caused by bacteria cause dieback of the stems. The use of copper-based sprays may reduce the problem.
It has been shown that the Naranjilla prefers semi-shade, a soil rich in organic matter with ample moisture during the summer. During the winter soil should not become waterlogged.
Naranjilla grown under the protection of trees which provide fertile litter, such as the Puriri, but not pine trees, and should be ideal for growing in this country.
What does the future hold? Naranjilla can be grown in New Zealand. Some plants have shown that economic results can be achieved. It seems a matter of plant selection to aim for a more disease-resistant type of plant.
Over the years, it has already been observed that the more spiny type (on leaves and stem) are more resistant to disease than those with smooth leaves. Recent introductions from Ecuador are under trial at the writer's farm.
A sweeter fruit type originally found in the Baeza area in Ecuador is now growing here. Other selections from higher altitudes in the Andes might hold a better future. Hybrid plants of Solanum quitoense x Solanum vestissimum may result in some interesting fruits.
Growing Naranjilla is one thing. The real challenge will lie in finding a market for the fruit.
DATE: September 1990
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