Growing Naranjilla Sustainably 

How A Distinctive Taste of South America Can Be Grown Sustainably, Keeping its Growers Healthier and Better Off…

On our tour of Ecuador, courtesy of The Adventure Traveller, we visited Carlos, a naranjilla farmer at Archidona in the foothills of the Andes.

Naranjilla, Solanum quitoense, is a short-lived tropical perennial related to tomato. It is native from Costa Rica to Venezuela and Peru. It is particularly popular in Colombia and Ecuador, however the farmers who actually grow this fruit work hard, don’t earn enough – and their health is put at risk by the unnecessary and costly use of chemicals.

Naranjilla produces juicy fruit widely used in making delicious thirst quenching – and very regional – juices.

I’ve grown naranjilla in subtropical Brisbane and found the juice goes well with celery, beetroot and apple. Naranjilla also makes a zesty gravy (not unlike tree tomato).

Australia’s blue-banded bees are excellent pollinators of this crop.

In Ecuador’s Archidona, naranjilla is grown in fertile, heavy clay volcanic soil in terraces cut into the walls of sheltered gullys. The climate is tropical, it’s around 500m above sea level, and rainfall occurs all year round

In this warm, moist, humid, frost-free climate, naranjilla gradually fruits itself to death! The crop is rain watered, and weeds are slashed down by machete. A planting will typically crop for around seven years.

Like many farmers, Carlos grows naranjilla in a simple polyculture. Growing balsa for timber and cassava for its starchy roots helps increase his income and these plants grow well together, providing shelter and light, dappled shade for the naranjilla.

Naranjilla fruit are wiped free of hairs, sorted by size, washed and packed in crates made from locally grown Cecropia sp., a leafy, fast growing native tree that is one of the first colonisers to appear after lowland primary rainforest is cut down or disturbed.

A Cecropia wood yard.
Sawdust from milling Cecropia is used to make mulched footpaths in naranjilla plantations.

Sawdust generated by making boxes is used to make mulched footpaths in the plantation.

Despite the relative ease of culture and heavy yield of naranjilla from the second or third year, the farmers get poorly paid for their work – the real mark up occurs at the point of sale. Many farmers would be familiar with this situation.

Carlos has grown naranjilla for forty years, he started farming them when he was 20 years old. His farm produces 200 boxes for a year’s work. This, plus the sale of cassava and balsa wood earns him A$1,600 (after tax) each year.

Unfortunately, Carlos, like many other naranjilla farmers, has been persuaded by agribusiness companies that buying their copper-based fungicides is the best way to produce healthy naranjilla fruit for the highest price. This too is a common situation for farmers.

Cecropia regrowth.
Cecropia is one of the first tree species to appear after primary rainforest is cleared or disturbed.

But in hot climates, few farmers like Carlos own protective clothing, let alone wear it. When asked why not, a common response is why would you work in discomfort, when you have been told the product is safe to use?

It was disturbing to learn that Ecuador’s naranjilla farmers suffer a high suicide rate, linked to serious depression, which is a consequence of long term exposure to copper, a toxic heavy metal.

It doesn’t have to be this way. Using safer solutions, you can grow naranjilla organically. Just as I have done in Queensland.

Naranjilla ready for market.
Naranjilla in Cecropia boxes ready for market.

Growing naranjilla sustainably

  • Common name/ scientific name: naranjilla, Solanum quitoense
  • Spacing: 2 – 2.5 metres;
  • Height: 2 – 2.5 metres;
  • Sun/ shade: six hours full sunshine. Avoid western sun;
Naranjilla, balsa and cassava polyculture.
Naranjilla, balsa and cassava polyculture.

Best climate zone

In Australia, the Atherton Tablelands is perfect, otherwise coastal tropical to subtropical Queensland and NSW. Naranjilla adapt to a frost-free, coastal, warm temperate climate, just expect seasonal cropping and smaller fruit.

Sowing / Planting time

Tropical, subtropical climate zones: sow October to November. For best results in warm-temperate regions, sow in September and raise the seedlings in an igloo.

Naranjilla is a prickly shrub. It’s primarily grown for its tart fruit which are used for juicing. Plants produce large, flimsy, short-lived leaves.

Ideal conditions induce heavy cropping for up to seven years.

Find a position offering six hours of full sunshine in winter that is sheltered from gales and the western sun. Some shelter is useful because cold or hot winds may induce fruit drop. It also encourages strong growth, good looks and large fruit.

The soil should be fertile, compost-rich, and well dug before planting.

Plant seedlings in mounds, or in raised beds, or grow in a pot, 50cm diameter or more.

Remember, the more sun plants receive, the more frequently they must be watered, but drainage must be excellent to avoid water hanging around which can encourage root rot:

  • Prevent pots from standing in water; 
  • Allow plants to go slightly dry in between each watering;

Flowering commences once plants reach about five months old.

Maturing fruit turn orange and in winter, they may be fully ripened indoors by sealing them in a plastic bag with a ripe tomato.

Copper residue on naranjilla.
Copper residue on naranjilla.

As always, save seed from the best performing plants. Since naranjilla likes a long summer, aim to select seed from the best of the early fruiting individuals.

Naranjilla are susceptible to a range of harmful root rot diseases. Starting with Pythium, Fusarium, Rhizoctonia, Verticillium and also Phytophthora. Chemical companies would encourage farmers like Carlos to buy and apply a systemic fungicide to control these pathogenic fungi. Without protective clothing, applying these chemicals is a health risk.

What makes naranjilla growing sustainable, is putting crop health and farmer’s health first.

Healthy naranjilla don’t get root rot disease

We know these plants prefer freely draining soil because in these conditions these diseases do not prosper. Observing the correct spacing between plants and avoiding heavy shade also help reduce the risk of foliar fungi.

Naranjilla, Solanum quitoense.
Naranjilla, Solanum quitoense.

Encourage excellent drainage by planting naranjilla in mounds, 25-50cm high. In my Brisbane garden, I grow them successfully in a raised bed.

A dish drain should be constructed around the top of the mound. This is a doughnut-shaped ridge of soil on a level mound. It creates a flat well. This prevents water – applied for example by hand using a bucket or hose – from running off, down the sides of the mound. The water is retained and percolates through the mound, drawing the roots deep into the soil.

If solid fertiliser, like rotted poultry manure or pelletised poultry manure (an economical and useful broad spectrum, aka ‘complete’ fertiliser), is added within the dish drain, the nutrients are retained within the root zone. Fewer nutrients are lost if heavy rain falls suddenly – a common situation in Archidona, which receives 4m rainfall.

Mounds with dish drains save water and reduce nutrient losses in runoff – the farmer gets value for money and effort, while less runoff keeps creek and river water cleaner

Foliage and fruit may be affected by fungal disease, mites and others.

Foliar disease is most common during warm, humid, calm, cloudy weather between autumn and spring, when drizzle and dew moisten the leaves.

Here are organic solutions to foliar diseases and pests.

1. My grandad’s home made organic fungicide is made by adding 1 level teaspoonful of bicarbonate of soda (baking soda) to a litre of water. Add one drop of dishwashing detergent and two drops of spraying oil. Common spraying oil brands in Australia include Pest Oil, DC Tron and Synertrol.

Apply the spray, wetting both sides of the leaves. The detergent spreads the bicarb evenly over the leaf surface, making it alkaline which frustrates the germination of disease spores. The oil fixes the bicarb to the leaf, so the spray is effective for up to three weeks. It offers the same length of protection as a copper-based fungicide.

Research at Sydney Botanic Gardens using my grandfather’s formula on roses during the late 1990’s (I managed Sydney Botanic Gardens, 1992 to 2003) proved this formula to be highly effective on a range of foliar diseases. Naranjilla farmers like Carlos will also find it is economical and completely safe to use.

Grandad’s formula has since been commercialised in Australia, where gardeners can now buy it conveniently at an inflated price. Make your own!

2. An alternative organic remedy for foliar fungi is applying a spray of wettable sulphur. This formula cannot be made at home, so buying it adds to the cost of production, however it is safe to use and very effective.

3. Sometimes, naranjilla foliage can be damaged by two-spotted mite during warm, dry weather. This can occur every year in Australia. Spraying with wettable sulphur is a traditional organic control for this pest.

Note: only apply wettable sulphur when the temperature is forecast not to reach 30C or more. Spray early in the morning on a calm, cloudy day.

4. Occasionally, naranjilla may be attacked by mealybug, scale insects and aphids. To avoid persistent, systemic pesticides you can spot spray individual plants rather than blanket spray the entire crop, using either pyrethrum or spraying oil. Spot spraying is a cheaper solution for the farmer.

Horticultural hygiene

Fundamental to success with naranjilla is horticultural hygiene. Treat naranjilla as tomato or eggplant in crop rotation plans.

Naranjilla is susceptible to root knot nematodes, which are difficult to control, so growing them in the same soil crop after crop encourages this pest.

It is possible to grow a break crop, like corn, after clearing a crop of naranjilla. Corn roots are not a host plant for root knot nematodes, so this starves this pest.

Ideally, where root knot nematodes are well established, clear the naranjilla, sow a break crop followed by a crop of cassava, another plant that root knot nematodes do not thrive on, before again planting naranjilla. 

Do not underestimate the value of regularly removing fallen naranjilla foliage as this may harbour disease and pest eggs. It is more than tidiness, removing dead and fallen leaves breaks the cycle of pest and disease repeating within the crop.

Sliced naranjilla.
Sliced naranjilla fruit.

Conclusion

Since the invasion of Ukraine by Russia in February 2022, global fertiliser, fossil fuel and pesticide costs have risen steeply, resulting in food inflation for consumers and a significant reduction in the already slim profit margin for farmers.

In my experience, no copper fungicides are needed to grow healthy naranjilla.

Currently, there is no consumer demand for an alternative to chemically grown naranjilla, but once the consumer knows there are alternatives, it is easy for them to make a healthy choice and to back sustainable naranjilla farmers who also do not pollute the environment with chemical or nutrient runoff.

Chemical-free, sustainably grown naranjilla grow just as well, their fruit is a comparable size if not bigger, and the cost of production is lower. It is possible for farmer collectives to sell organic naranjilla at the same or a higher price, increasing farmer’s income.

Witoca organic coffee growers’ Fair Trade Collective.
Witoca organic coffee growers’ Fair Trade Collective have re-trained coffee growers and rebranded their product so growers earn a better income and a have safer working conditions.

Not far from Carlos, is the Witoca organic coffee growers’ Fair Trade Collective . These small scale farmers have demonstrated how to re-brand their product to attract the health conscious consumer with a product that is healthier to drink and more profitable for the farmers to grow.

This collective is also training and encouraging young people to remain on the land and to grow organic coffee, reversing the trend of rural depopulation, documenting their successes as evidence that small scale farming can be safe and profitable.

No farmer should ever put their health or their life at risk simply to earn a living.

Jerry Coleby-Williams 

Director, Seed Savers Network
11th January 2023

2 Comments Add yours

  1. Amal Fahd says:

    Hi Jerry, Can you please do a post on foods/herbs that you grow that are highly nutritious and how to grow them?  It looks like you grow a lot of food and some that are unusual. I enjoy your segments on Gardening Australia. Regards,Amal

    1. Please keep to topic and use the email facility provided to ask questions.
      Food and herbs? First read my ‘In Production Today’ posts and other posts involving Food Production over the past five years. Thank you. This comment will be deleted tomorrow as it has no connection to naranjilla.

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