PERFORMANCE OF LONGAN
ON THE ATHERTON TABLELAND OF NORTH QUEENSLAND
SCIENTIFIC NAME: Euphoria longana
FAMILY: Sapindaceae
ABSTRACT
The longan is one of the most important fruit crops in Thailand and a number of authorities consider it to have potential for commercial development in similar climatic zones of Australia.
Twenty longan cultivars have been imported since the 1970s and are currently being evaluated at Walkamin Research Station on the Atherton Tablelands of North Queensland. Data is presented on yields and fruit quality. Problems for potential growers are discussed.
INTRODUCTION
The longan, a member of the Sapindaceae family, is an evergreen tree native to southern China and several other areas of southeast Asia (6).
Today, longans are a major crop for Thailand (1, 2, 5) and to a lesser extent in the Fujian and Guangdong provinces of China and in Taiwan (2). Thailand is the world's largest producer with 27,000 ha (2), which is somewhat surprising, as the first longans were only imported from China to Thailand in 1896 (1). Daw is the earliest and most widely-planted selection in Thailand, although others bring better prices (1).
Longans today are also grown in both Hawaii and Florida, although neither area has what could be deemed a commercial industry.
Longans may have been originally introduced to North Queensland in the last century by Chinese miners. Although trees have been in North Queensland and other areas of eastern Australia since that time, a commercial longan industry has yet to develop. Most selections introduced in the early days were thin-fleshed with large seeds, i.e. poor quality.
To help determine the potential for longans in Queensland, the Queensland Department of Primary Industries via Brian Watson at Kamerunga Research Station near Cairns, commenced an introduction and selection programme in the late 1970s. Five cultivars from Hawaii, 2 from Florida, 5 from Thailand, 5 from China/Hong Kong and 3 from Taiwan have since been introduced by both the Queensland Department of Primary Industries and New South Wales Department of Agriculture.
This paper is a progress report on the performance of longan selections on the Atherton Tablelands.
METHODS AND MATERIALS
Currently 20 introduced, as well as one local selection, are being evaluated at Walkamin Research Station on the Atherton Tableland (17.8 degrees south, 591 m elevation), ( Table 1). The soil type has a basaltic origin characterized by low phosphate and organic matter.
Table 1. Origin and Plant Introduction Numbers of Longan Cultivars Under Evaluation
| Origin | Introduction Number |
| Thailand | |
| Biew Kiew | 14909 |
| Chompoo (See Chompoo) | 14911 and 13204 |
| Dang (E. Dang) | 14910 |
| Daw (E. Daw) | 13203 |
| Haew (E. Haew) | 16281 |
| USA Florida | |
| Homestead | 13201 |
| Pon Yai | 12400 |
| USA Hawaii | |
| Fuhko 2 | 13304 |
| Ilao (E. Ilao) | 12809 |
| Kay Sweeney | 13900 |
| Kohala | 11789 |
| Wai (E. Wai) | 12810 |
| Taiwan | |
| Chien Liou | 13765 |
| Duan Yu | 13764 |
| Fugan (possibly seedling) | 13965 |
| China/Hongkong | |
| Fa Hok Chai (seedlinqg) | 13547 |
| Saig Geeb | 14674 |
| Shek Yip | 12594 |
| Shi Xia | 17898 |
| Wu Yuan | 17897 |
| Local | |
| Birch (Cardwell Large) | |
Detailed data has been compiled since 1982/3 on time of flowering and fruit set, yield and fruit characteristics. Yield data has been adjusted to compensate for major losses to parrots and fruit bats. Average fruit weights and percent recovery (% aril) are being determined on samples of 50 fruit; fruit length and width on samples of 25, while brix is determined on 10-12 fruit samples. All fruit are sampled randomly.
Eight cultivars are represented by 2 tree plots. Data from these trees has been taken separately but meaned in this report. Other cultivars are represented by single tree plots.
Fruit are sized and graded by passing a maximum 2 kg sample through sieve orifices of 32, 25, 22 and 19 mm diameter.
Fertilizer and water regimes are those recommended for lychees in QDPI lychee crop summaries for North Queensland. Until 1986, no pruning was conducted. Recently, the more vigorous, upright-growing selections such as Kohala and Homestead have been topped.
RESULTS
Yield (Table 2)
With the exception of Pon Yai, all trees have established satisfactorily, with detailed yield data being compiled since 1982/83. Data has been obtained from 18 selections. The most recent introductions - Shi Xia, Wu Yuan and Fugan are yet to crop. Most selections commenced cropping 3-4 years after field planting.
Five to six years of data has been collected on Biew Kiew, Chompoo I and II, Dang, Daw, Duan Yu, Haew, Homestead, Kohala, and Pon Yai. All have cropped irregularly with distinct 'on and off' years. At best, these selections have had 3 'on' years in the 5-6 seasons of cropping. Considerable tree-to-tree variation has been observed in the two tree plots; in some years, only one of the trees has cropped.
Table 2. Yield Performance of Longan Cultivars at Walkanin Research Station
| Yield+ (kg)/tree | |||||||||
| Cultivar | Year Planted | 1982 | 1983 | 1984 | 1985 | 1986 | 1987 | 1987 | Comments |
| Biew Kiew | 1979 | - | 0.5 | 3.9 | 7.6 | 55.6 | 0.0 | 72.6 | |
| Birch (Cardwell Large) | 1984 | - | - | - | - | 0.4 | 0.0 | 5.0 | |
| Chien Liou* | 1980 | - | - | - | 4.8 | 3.5 | - | - | Removed 1986 |
| Chompoo I* | 1978 | - | 42.9 | 5.5 | 62.0 | 9.9 | 0.5 | 33.3 | Heavy parrot/bat loss |
| Chompoo II | 1979 | - | 0.5 | 0.0 | 5.6 | 66.2 | 3.6 | 10.5 | Heavy parrot/bat loss |
| Dang | 1978 | 0.5 | 22.3 | 0.6 | 16.6 | 4.0 | 1.0 | 29.5 | Heavy parrot loss |
| Daw * | 1979 | - | - | 0.15 | 1.6 | 0.65 | 0.5 | 2.6 | 1 tree removed pre-harvest |
| Duan Yu | 1982 | - | - | 0.7 | 22.0 | 3.8 | 0.1 | 54.4 | Only half tree cropped 1988 |
| Fa Hok Chai | 1984 | - | - | - | - | - | - | 5.0 | All lost to parrots |
| Fuhko 2 | 1984 | - | - | - | - | - | - | 7.6 | |
| Haew* | 1979 | - | 9.9 | 0.15 | 19.7 | 4.5 | 2.0 | 13.7 | |
| Homestead I and II* | 1981 | - | - | 0.3 | 1.2 | 23.2 | 0.6 | 18.1 | Heavy parrot/bat loss |
| Ilao | 1983 | - | - | - | - | - | 4.1 | 17.5 | |
| K. Sweeney* | 1983/84 | - | - | - | 0.13 | 0.8 | 0.0 | 10.5 | Heavy parrot/bat loss |
| Kohala* | 1980 | - | 1.4 | 1.7 | 19.5 | 21.2 | 8.8 | 41.8 | 1 tree only cropped '86, '87 |
| Pon Yai* | 1982 | - | - | - | 0.3 | 5.2 | 0.0 | 1.4 | |
| Saig Geeb* | 1985 | - | - | - | - | - | - | 3.8 | |
| Shek Yip | 1983 | - | - | - | - | - | - | 1.65 | |
| Wai | 1983 | - | - | - | - | - | - | 2.4 | |
* Mean of two trees
+ Yields adjusted to compensate for fruit bat and parrot losses
Maximum yields have been with Biew Kiew and Chompoo I (72 and 76 kg of fruit on 9 and 6-year-old trees). Daw, which is the most popularly planted cultivar in Thailand, has had a maximum yield of 2.6 kg on a 9-year-old tree.
Mean yearly yields per tree during this period have been Chompoo I 25.7 kg, Biew Kiew 23.4, Duan Yu 16.2, Kohala 15.7, Chompoo II 14.4, Dang 12.7, Homestead 8.7, Haew 8.3, Pon Yai 1.7, and Daw 1.5.
Two to three year's data have been obtained on Chien Liou, Birch, Ilao, Kay Sweeney and 1 year's data on Wai, Fa Hok Chai, Saig Geeb and Shek Yip. It is too early to draw meaningful conclusions on yield patterns or capacities from this limited data.
The selections under evaluation can basically be divided into early-, mid- and late-season longans. Early-season cultivars include Kohala, Homestead and Kay Sweeney, which mature in late January to early February. Mid-season types include Daw, Duan Yu, and Pon Yai (mid-February). Biew Kiew, Chien Liou, Chompoo, Dang, Haew are classified as late-season, ripening in March or April depending on the year. Insufficient data has been obtained to classify other selections. Kohala, Homestead and Kay Sweeney are much earlier than the Thai selections, including Daw.
Fruit Quality (Table 3)
Data on fruit characteristics has been secured since 1983. Average fruit weights range from 6.2 g for Birch to 12.5 g for Kay Sweeney. Kay Sweeney, Biew Kiew, Kohala, Saig Geeb and Homestead have been the only selections to have a mean weight in excess of 10 g.
Mean % flesh recovery (% aril) has varied from 55.9 (Birch) to 72.2 (Kay Sweeney). Most recoveries are in the low to mid 60s. In general, larger-fruited selections have a greater % aril than smaller cultivars. Year to year variation in recoveries has, in general, been minimal.
Total soluble solids as measured by brix levels have averaged 18-21%. Chien Liou was the one exception with a mean brix of 10.3%.
Flesh texture of the Thai, Florida, Chinese and Hawaiian selections, which have cropped, can be described as crisp. The Taiwan and local selections are soft-fleshed.
Eating quality or flavour can best be described as "morish" with most cultivars having a sweet taste. The Thailand selections, in general, had the best flavour and eating quality. Crisp-fleshed selections were felt to be more desirable to consumers than soft-fleshed lines. Overall, the early-season types i.e. Kohala and Homestead, while having an acceptable eating quality, were not rated as highly as the later-season Thai types. Ilao, another early type, has a flavour and eating quality similar to the late types. Saig Geeb and Shek Yip were excessively dry.
Table 3. Fruit Characteristics of Longan Cultivars at Walkanin Research Station
| Mean Fruit | ||||||||
| Cultivar | No. Years Data Collected | Weight g | Length mm | Width mm | % Aril | % Brix | Flesh Texture | Comments |
| Biew Kiew | 5 | 11.5 | 25.6 | 28.0 | 64.9 | 20.9 | Crisp | Excellent quality |
| Birch (Cardwell Large) | 2 | 6.2 | 21.3 | 20.8 | 55.9 | 19.6 | Soft | Sweet, poor quality |
| Chien Liou* | 3 | 8.3 | 23.4 | 23.9 | 58.4 | 10.3 | Soft | Many parthenocarpic fruit, small, poor quality |
| Chompoo I | 5 | 9.4 | 23.7 | 25.8 | 64.4 | 19.7 | Crisp | Sweet, good flavour |
| Chompoo II | 5 | 8.7 | 24.4 | 26.2 | 62.6 | 21.5 | Crisp | Sweet, good flavour |
| Dang | 5 | 9.4 | 23.5 | 25.6 | 63.4 | 19.9 | Crisp | Sweet, good flavour |
| Daw * | 4 | 9.6 | 24.3 | 25.8 | 60.9 | 19.2 | Crisp | Sweet |
| Duan Yu | 5 | 9.5 | 24.1 | 25.4 | 58.3 | 18.1 | Soft | Thin flesh, far quality |
| Fuhko 2 | 1 | 7.6 | 23.4 | 24.4 | 57.0 | 20.6 | Semi-Crisp | Sweet |
| Haew* | 4 | 9.5 | 23.8 | 26.4 | 63.3 | 19.6 | Crisp | Sweet, good flavour |
| Homestead I and II* | 4 | 10.1 | 24.0 | 26.4 | 63.3 | 16.3 | Crisp | Mild flavour |
| Ilao | 2 | 9.3 | 23.2 | 26.7 | 68.5 | 20.8 | Crisp | Sweet, flavour like late Thai types |
| K. Sweeney* | 2 | 12.5 | 25.8 | 28.4 | 72.2 | 16.5 | Crisp | Sweet, mild |
| Kohala* | 5 | 10.5 | 24.5 | 26.9 | 68.6 | 17.7 | Crisp | Sweet, mild |
| Pon Vai* | 2 | 9.0 | 23.6 | 24.9 | 6.3 | 20.0 | Crisp | Variable size and quality |
| Saig Geeb* | 1 | 10.3 | 26.2 | 26.6 | 68.3 | 16.1 | Crisp | Sweet, very dry |
| Shek Yip | 1 | 8.8 | 24.3 | 25.9 | 65.0 | 14.6 | Crisp | Sweet, very dry |
| Wai | 1 | 7.8 | 22.8 | 24.5 | 60.8 | 19.2 | Soft | Sweet |
* Mean of two trees
Samples based on means of 25 fruit for length and width, 10 for brix and 5 for weight and % aril.
Fruit Size (Table 4)
Fruit sizes varied considerably. Only a few fruit were retained on a 32 mm screen with Kay Sweeney being the only cultivar with any meaningful percent of fruit in this category (7% by number and 10% by weight).
Table 4. Size Distribution of Longan Cultivars at Walkamin Research Station
* Mean of 2 trees
Size based on passing samples through sieves having orifices of 19, 22, 25 and 32 mm
Biew Kiew and Saig Geeb had large percentages by weight and number falling into the 25-32 mm range. Birch, Chien Liou and Pon Yai had large amounts falling into the smaller size. Shek Yip in its first year of cropping, also had a large amount in these categories. Ilao also had a significant amount in the smallest size, however this was in its first season when a large amount of fruit was parthenocarpic, especially Chien Liou.
PROBLEMS
Longans at Walkamin have proved very susceptible to a number of pests, including elephant beetle, fruit bats, and birds, especially parrots. These pests have on several occasions drastically reduced harvested yields or caused total losses in some trees.
A number of minor insect problems such as peach moth have occurred, but in general, have not been of major consequence. Pon Yai has proved very susceptible to pink wax scale and sooty mold.
A heavily laden Biew Kiew tree yielded approximately 55 kg of fruit but failed to crop the following season. It was netted for protection from fruit bats.
Daw, one of the more popular Thai cultivars, has a pollination, or setting problem, which has occurred year in year out and also at another trial site. This problem has not been evident with any other cultivar. In Thailand it is noted as the most consistent bearer (2).
In 1986, winter conditions were extremely mild for Walkamin, and the crop failed except for a small amount of Kohala.
Some incompatibility problems with grafted trees are evident, but rootstock/scion combinations have not been studied to any extent.
DISCUSSION
Yields as evidenced in Table 2 have generally been disappointing, even if the crops hadn't been attacked by birds and fruit bats. A trend toward irregular bearing has become evident with many cultivars. Yields have not been comparable to those reported from Thailand (6) of 120 kg per tree for trees of all age groups in one year.
In the seasons with light crops, only a small percentage of floral terminals were produced. This is responsible for the low yields in most instances. Similar problems have been noted in Thailand (1).
It is possible that better size and more regular cropping could be obtained by flower- and fruit-thinning in 'on' years and flush-thinning in 'off' as is recommended in Asia (2, 7). However this is not considered a viable proposition in Australia because of our high labour costs. No selection to date has exhibited a regular cropping pattern, which must raise doubts about the economics of longan production under the present management system.
In Florida (3), no selection has been found which fruits regularly. On a given tree, good crops occur only one year in three or four. Cropping in Thailand is also noted as varying considerably from year to year (2, 6), with one poor, one fair and one excellent crop in a three-year period. Biennial bearing also occurs in China (7).
From a quality view point, soft-fleshed selections are less desirable, thus Birch, Chien Liou, Duan Yu and possibly Wai (1 year data only) should not be considered for planting.
Fruit size is important, and fruit should be left on the tree as long as feasible as there is some leeway in time of harvesting.
From a marketing view, the authors feel that only fruit being retained on a 25 mm screen would be seen as top-quality. 22-25 may be satisfactory for seconds, but smaller sizes should be discarded.
Ilao - A promising new early season cultivar. Ilao is smaller than the other early-season fruit but possesses a flavour similar to late-season Thai selections.
Hence when looking at Table 4, a number of selections can be eliminated due to their size. Some year-to-year variation of sizes has occurred, but generally this has been slight. Birch, Chien Liou, and Pon Yai can be eliminated on size, while further data needs to be obtained on Fuhko 2, Shek Yip and possibly Ilao before decisions can be made. Chompoo II and Daw would have to be questionable from a size classification, as too many fall into the unacceptable size areas.
The limited amount of Australian data published thus far (4) suggests larger fruit sizes (13-17g) than that reported here. Only the largest fruit in Table 4 would be comparable, suggesting that only the largest fruit have been reported in that paper. The number and percent of fruit in each size category, as presented in Table 4, is felt to be a preferable method of reporting fruit size.
Also with regard to marketing, selling fruit on the panicle after post-harvest dipping and bagging in plastic, should be investigated. Labour costs are reduced, as removing fruit from panicles is a major time-consuming exercise. Machines to snip fruit from panicles need researching. A small amount of trial fruit was marketed locally last year, with superior prices received for fruit retained on panicles as compared to loose fruit.
Post-harvest sulfur dioxide treatments have shown promise.
Initially, trees were not pruned, as the objective was to observe how the trees grew. However topping of the more vigorous upright types, eg., Kohala, Homestead etc., is highly recommended as well as skirting, as fruit along the ground are of poor quality, and low limbs interfere with normal cultural operations. Reducing the number of main branches to 3-5 and opening of the centres should also be investigated.
CONCLUSIONS
Cultivars such as Birch, Chien Liou and Duan Yu cannot be recommended due to poor fruit quality (flesh texture, flavour and size), while Daw and Pon Yai fail from a yield viewpoint. The more promising cultivars under Walkamin conditions are:
Biew Kiew
Ilao (subject to further data)
Kohala
Kay Sweeney (subject to further data)
Haew
Chompoo I
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References
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DATE: March 1989
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