Acotanc: Fruits and Nuts in the Tropics of Australia

Fruits and Nuts in the Tropics of Australia

Author: Bruce Toohill
Organization: Mango Farm
PO Box 946
Katherine NT 0851

A description of the history and current situation of the tropical tree crops grown in northern Australia.

I am actually a mango grower these days; we have 40,000 mango trees at Katherine in the Northern Territory. The Northern Territory is not a state, but a territory, sometimes confused with the Northwest Territories of Canada in the mail.

Everything north of the Tropic of Capricorn is the tropical part of Australia. From Broome on the west coast across to the dry tropics of the Queensland coast is the semi-arid region. Virtually all of our northern part is dry tropical or semi-arid, apart from the humid, or wet tropical area around the Atherton Tablelands and a few pockets down the coast. Further down the Queensland coast is the sub-tropics, and it is humid there, as well. Our environment is characterised by a short wet season and usually a very hot dry season.

What I wish to talk to you about is to give you some idea of what is happening in a commercial sense across that area. I looked back into the proceedings of the 1982 meeting of this organisation which was the first ACOTANC Conference, and at which I was a speaker. I talked a lot about potential, and that was 20 years ago. In those days there weren't many people in this northwest corner of the country. Today it is a different story. Quite a few things have happened in the last 20 years, so I want to share some of those with you.

The most important tree crop up there is the mango. Eighty percent of the plantings are of the one variety, Kensington Pride. It is polyembryonic, so it actually doesn't have to be grafted. But to grow it in the dry northwest tropics, we found that we have to graft to get more regularity out of our production. The figures show that a few years ago there was a total of about 1.5 million trees. Now there is about 2 million trees in the ground, and still expanding. In the Northern Territory, the figure of 400,000 has become more like 600,000 trees. Two-thirds of those aren't yet fruiting. So, in the next two or three years, there will be a major production increase from that part of the world. Fortunately, we have a seasonal advantage, where the Northern Territory is the earliest to produce, together with Western Australia. As you go further south, the season becomes later and later. It actually fits in nicely with a consistent production cycle, and we end up with fruits being available on our domestic market from late September to April, if you include Gingin, just a little north of Perth. It is thought there are about 10,000 trees in the ground there at the moment. These areas are more frost-prone, so you have to find frost-free sites, with a slope to drain the cold air. If you do have an unseasonal frost which burns off your flowering, the extreme cold (at least as far as the mango trees are concerned) means that more lateral buds are formed that can come out later on. In northern areas, that ability doesn't occur: it is a purely terminal-flowering tree, and if for some reason you lose it, you don't get a second bite at the cherry.

There have been a few other varieties tried. The Americans and South Africans will know about the Florida varieties that were selected over the last 100 years. Some of those find some sort of a niche in Australia. The R2E2 is, in fact, a seedling selection from a Kent parent tree that had Kensington as a male pollinator, producing a fruit that is 600 to 900 grams in weight, a large fruit. The Chinese, in particular, like it, and it is just beginning to become commercially planted. There is a range of others under assessment.

The second group of fruit of note is citrus. One particular one is grapefruit. Traditionally, grapefruit is grown in the southern part of Australia. The riverland along the borders of Victoria and NSW and South Australia is a typical growing area. The result is that since it is a tropical fruit, really, it is a very acid fruit. Older Australians are used to having sugar on their grapefruits. Younger Australians couldn't care less. We are now looking at growing grapefruit where it should be grown, which is in the tropics. We are looking at the red-fleshed grapefruits, all of which, except for Star Ruby, have come from the southern United States. We are looking at a range of performance on a range of rootstocks. With citrus, there has been a lot of research done on scion/rootstock performance. You can't avoid having to do that in your own environment, particularly in a new environment.

The reason we are looking at the range of fruits: if you compare a temperate environment with a sub-tropical and a dry tropical environment, the sugar to acid ratio increases dramatically. The fruits with those sort of figures are far more palatable.

There is a range of other fruit trees coming into the scene. Kaffir Lime (Citrusis grown extensively in the top end for its leaf, for the Asian market, their cooking.

There are about 5000 rambutan trees,Nephelium lappacceum,in the Northern Territory, and about 15,000 in Queensland. Again, the NT fruit comes in before the Queensland fruit, so there is continual production. The eating pleasure of rambutans is quite dramatic. It is related to lichee, to my mind less sweet than lichee. There are cling stone and free stone varieties. There is one particular problem, and that is that the birds love it, the parrots. We have found over the last decade that the only hope of growing it is under bird netting. There was an initial expansion of plantings that declined when people realised the problem. In the last three years, NT growers have combined with Queensland growers into a marketing organisation which has now gotten them into the Japanese market, and plantings are just starting to expand again.

The lichee, Lichee chinensis,is more suited to the cooler parts of the Queensland coast. There is one single planting of about 10,000 trees, north of Ingham, just north of Townsville, so it is just getting into the wetter tropics. They are primarily concentrating on a variety known as the Kwai Mi pink, or B3, because it was found by Herb Bosworth in a back yard in Cairns just before the developers knocked over the 4 or 5 trees that had probably been there a hundred years. He propagated them all, looked at them, and found that the Kwai Mi pink was a low-chill variety, so that has formed the basis of a lot of the northern plantings. It was very fortuitous that he got there first. One of the problems with the lichee is the inconsistent flowering on the coastal climate of Queensland. So in many of the parts where it is grown, it is quite inconsistent from season to season. About ten years ago I happened to be down in Gingin looking at mango trials, and found a little later there was a planting of tropical fruits closer to the coast in which there were a hundred or so lichees. The remarkable thing about that was that the lichees flowered beautifully. They didn't hold much fruit, unfortunately. I think in recent years there have been some other plantings up in the hills, and some UWA students have had a look at it to try and work out the pollination problems that were occurring. These trees in the hills have, in fact, held fruit to maturity. So, as long as you can grow the tree, they find, that as with mangos, a warm, northern-facing slope that is relatively frost-free, you could have a niche growing point here. Lichees are actually more cold-tolerant than mangos. When the Chinese find out that there are fresh lichees available for the Chinese New Year, they will be very, very happy.

The durian, Durio zibethinus, is a true tropical from Malaysia, Indonesia. This is the king of the fruits as far as many of those people are concerned. It has a very woody external husk. If you walk down the street in any town in south east Asia with a couple of those swinging by your side, and you happen to be looking somewhere else and someone gets hit by them, you can get a great stream of abuse, because they are extremely sharp. The flesh is a very strong flesh, custard-like. Most Asian people absolutely love it, and most Europeans can't stand the stuff. It is a heating fruit, so if you are sitting eating it with a group of Malaysians, you have to follow it with a cooling fruit to get your metabolism back to normal. They follow it with mangosteen. There are plantings in the wet tropics of north Queensland, perhaps 15,000 to 20,000 trees and perhaps 5000 trees around Darwin, not yet fruiting. There is a long lead time to production, and they are just starting to put some fruit on the Australian market place. As you move north from south Malaysia to about Bangkok, which is the northernmost point of the germplasm range, you move away from an extremely, strongly-flavoured, bright yellow-coloured flesh, to a much whiter, blander flesh and a larger fruit. The Thai varieties that have been commercialised from that northern gene pool have quite a different taste sensation to the Singaporean, Malaysian and Indonesian varieties.

Custard apples, Annona spp., are a little bit out of their range in my part of the world, but they are certainly to be found in the cooler parts of the coast. Custard apples are essentially restricted to the east coast. People have tried them in the north west and not done terribly well.

The mangosteen,Garcinia mangostana, a remarkable fruit, in my opinion, probably the best fruit in the world: I hope you all get a chance to eat it some day. This is the mangosteen. The mangosteen is a truly tropical tree, an understory rainforest tree. To my mind, probably the nicest fruit that comes out of that district. We have about 3000 trees in the Darwin area, of which one planting has 2500 trees, so there is not that much around. There are probably about 10,000 in North Queensland. The difference is that the N. Queensland plantings are all in the wet tropics and our plantings are all in the dry tropics. Some of them are under bananas to provide a microclimate. Others have been under Ice Cream Bean trees, Inga spp., as a shade crop. Yet others are out in the open. Some are painted with acrylic white paint to reduce sunburn problems. Twenty years ago when I planted the first one at the labs in Darwin, no one thought we had a chance. The methodology of growing them in that part of the world is starting to come out, and I think the prospects are actually quite good. Certainly fruits are now available right down the east coast from the Queensland plantings and are receiving a very good response.

You can see the large flesh in the fruit in the middle. The segments are like a mandarin. The largest of them will have a seed, the others generally don't. The aril or the husk has a red pigment in it which stains everything it gets on, so you need to be careful how you handle them. The eating sensation of the flesh is just indescribable. So, go out and get one.

Star apples,Chrysophyllum caimito, are a large industry in the Philippines. There are just small plantings in the northern part of Australia that cater to the Philippine community around Australia.

Carambolas, Carambola averrhoa, probably have a niche market, but are probably not mainstream potential at the moment.

Avocado,Persea americana, is quite an established industry around Australia, including south and north of Perth, which wasn't there 20 or 25 years ago. In our part of the world, the standard varieties of avocado virtually won't flower--it is too hot. There are three gene pools from Central America: the Guatemalan; the Mexican; and the West Indian. The West Indian gene pool handles the hottest environment. Some years ago the CSIRO imported West Indian genetic material. I planted that at Kununurra. Fortunately some of that survived and we have had some fruit from it and identified a couple of varieties which are able to fruit in that environment, which is quite a new phenomenon. You must recall that the horticultural traditions of this part of Australia are pretty limited. They haven't had a lot happening there until the last 20 years. These are the two West Indian Avocado varieties I mentioned. The Semel 34 is probably going to be the variety of choice for the main production, and will be supported as a pollinator by the Victoria, which is a much larger fruit, and fewer fruits per tree. Avocados are not very good pumps, so to get the moisture up to the height of the tree you have to go to some trouble to get the right microclimate effects. Heavy mulching and windbreaks are standard for those varieties.

Longan,Euphoria longana, is another sapindaceous fruit that is extremely popular in southern China and Thailand. There is a little bit of that, and increasing interest in planting it.

The cashew, Anacardium occidentale,native to Brazil. You see cashews littering the countryside in Brazil like the eucalypts do in Australia. There is a tremendous demand for the apple of the fruit, which is used as a fresh fruit or for juice, just as we use orange juice. They distill it into an absolute rot-gut liquor, and produce both still and carbonated juices as well. The cashew is rather astringent, so that when you eat the apple, which is the red section (not a true fruit: the true fruit is the nut which hangs below it, so the apple is simply a swollen peduncle) it is quite juicy. If you don't have the right selections, you have a very astringent fruit in your mouth.

We have looked at it across the northern part of Australia in the last 20 years, with pilot farms and genetic improvement programs. Right now, there is only one operator in Australia, in Dimbulah, west of Cairns, in a dry, tropical environment. A fellow there, who also grows macadamias, has commercialised it on a limited scale. For our economy, it is a difficult thing, because it doesn't yet lend itself to mechanical harvesting. If you go to places like Kerala, you see big factories with people sitting crosslegged on the ground, with a hammer and a block of wood, a pile of unshelled nuts. Some of them have got their fingers wearing away because the liquid in the shell has a very corrosive effect. It is used in paints and for keeping the hulls of boats clean. We haven't found a way to make commercial success out of growing it. We certainly can grow it.

Pitaya, Dragon Fruit, Hylocereus ondatus,is a delicacy in Vietnam, in particular. There is a grower in Darwin who has quite a few thousand plants, and is hopeful of $7 or $8 per kilo for the fruit, and also selling plant material to other growers. It is like a cactus plant, easy to propagate. It is quite productive, has beautiful flowers. When you open that fruit, you have a white flesh with a very large amount of very small black seeds spread right through the flesh. So, it looks beautiful, and the Vietnamese like it. I think it will take some time for the general community to go for it.

I also want to just mention Noni, Morinda citrifolia,and Kakadu Plum, Terminalia ferndinandiana. Kakadu Plum is a species across northern Australia, a bush food, very acid, most of them. Occasionally, if you go down to Broome, you can go out with the local kids and they will take you to a trees around Christmas time which are reasonably sweet. It has been found that it has the highest Vitamin C content of any known fruit in the world. The Glaxo company is setting up a pilot farm in the east of Darwin, on the Arnhem highway, just west of Kakadu Park. Down at Broome we call it 'gabinj,' which is the local name. It used to be known as the Billy Goat Plum, but in this marketing and development program they have turned it to Kakadu Plum. The great challenge, if you like, is to actually get the right genetic material. So, their first exercise is to collect material from right across the north, evaluate it, and begin the process of genetic improvement.

Table grapes aren't particularly known in this part of the world, but we have about a hectare of table grapes we will be expecting a crop off this year on our mango farm in Katherine. The variety we are looking at is one of the hybrids that was produced by the CSIRO in Mildura back in the '70s and '80s. It is fairly widely grown now in California, but not very much in Australia. The interesting thing about table grapes in our part of the world, because we don't have a winter to speak of, therefore we don't have a dormancy, we can decide when we are going to harvest just by deciding when we are going to prune. About 120 days after pruning, we will harvest. We will be looking to prune these in early May for a late August, early September harvest, which is a perfect time because the Australian crop is well and truly over, the last fruits coming out of cold storage somewhat inedible, and the new crop hasn't come in yet. Still, at the moment, fingers crossed, the quarantine people are keeping the Americans out so there is no American fruit coming in, so there is a nice little window there. We will be looking forward to taking advantage of it. The variety in question is the Murray seedling on the left.

Jackfruits were mentioned by our friend from the Philippines, and there is a small industry in northern Australia. Large fruit. Again, it is a certain specialist market. More Australians can handle this fruit than they can the durian. You can get varieties which have a soft flesh, and they dry very well. You can also get varieties that have a very firm flesh, which generally, you would eat fresh. That is a relative of the jackfruit, of which there are very few up our way. It is a velvet fruit.

Moving away from fruits for a moment, I just wanted to mention a handful of plants, woody perennials, that are being grown in the north. This is a nursery of sandalwood, Santalum album, so it is from India and some other parts of Asia. Whereas, in Australia, the typical one that grows in the environment where the industry was based is Santalum spicatum. Which basically has been flogged out and is an example of a non-sustainable industry. The intention here with Santalum album is to plant it in the Ord under flood irrigation. It is a parasitic plant, so it requires a host plant to look after it and it produces a root that grabs around the root of a passing, unsuspecting host plant, and draws its nutrient supply from that. Over the last 20 years there have been a whole range of host plants evaluated in that environment, and that selection has been narrowed down to a handful of species, where they are also trying to get a commercial yield off the host plant as well. The cycling time for these was initially thought to be as little as 15 years, but it is probably going to be more like 20 to 25 years. Unlike the local species in southern WA, Santalum album has a very high oil yield. You have the heartwood incense sticks and so on, and you have the essential oil you can extract and use in a variety of ways.

A few years ago, someone unearthed a report from a member of the South Australian government that was published in 1922, stating that Melville Island, off the north coast of the Northern Territory, would be a good place to start a timber industry. That is now getting underway. It didn't take quite as long as the railway line, but it is good that it is happening. The interesting thing about it is that it is a joint venture with the Aboriginal people of the Tiwi Islands and the company, APT, based in Perth. They have Blue gum plantings south of here, and they have set up a joint venture company called Silviculture Pty Ltd. They are getting underway with doing it, having tested the species already. In excess of 30,000 hectares of Acacia mangium, to be planted for woodchips. Now Acacia mangium grows through several countries in south east Asia. Most of the genetic material they have planted they tell me is from Indonesia. It is a pioneer rainforest species, and grows all along the east coast in the northern half of Queensland. It was traditionally not considered very useful for timber, but nowadays if you live in the wet tropics of north Queensland, and you have a block of land that might have a single Acacia mangium out in a paddock of grass or something, the millers in that area go around looking for trees and they will pay you handsomely for it. Its timber is very valuable, it is a hardwood and it is scarce. The reason they have chosen this place is because of the 1800 mm rainfall. Darwin is about 1600 mm, where I live in Katherine is about 900 mm, although last wet season which just ended was probably the best one in about 30 years: we had about 2000 mm. The soils are very good, better than on the mainland, and the distribution of the rainfall is longer, so the long dry spell is shortened. It showers almost any month of the year, with the predominant rainfall being in the wet season.

There is interest going back to the mid to late '60s by the Commonwealth government through its Forestry and Timber Bureau, which no longer exists. It was taken over by the CSIRO Forestry division. They have been looking at planting timber trees up that way. They had trial plots all over the place. They introduced Pinus caribbea, from the Caribbean. They estimate they have got 300,000 tonnes of timber there, and they will be harvesting it shortly. They did a little bit of harvesting of it for things like grape trellises for South Australia, but most of it is in the ground. They do have a problem with adequate investment and infrastructure, and they are obviously expecting that once this joint venture is underway, they will have a deep-water port off the north coast of Melville Island that will take 50,000 tonne ships. They are looking to have an improved road infrastructure to be able to access these materials.

Native cypress (?) grows all across northern Australia. Queenslanders have better stands of it and they have an industry with it. The CSIRO planted plantings of that which grew slowly. It is fire-prone so it gradually got diminished by wild fires. Apart from the timber, it has an essential oil which a company was extremely keen to extract for the perfume market. As they found out, some of the components of the essential oil were unstable, and therefore didn't suit the perfume trade. So they are going for essences. They produced 37 litres for the Olympic Games, so those of you who were there may have bought a little vial of it as the Essence of the Games, as it was marketed. It is very valuable: $300 per litre, but you can see that you need a lot of trees to extract it. So, that is getting underway.