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Fig. 38: Pummelos (Citrus maxima) vary in form, size, color and flavor of pulp.
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The pummelo tree may be 16 to 50 ft (5-15 m) tall, with a somewhat crooked trunk 4 to 12 in (10-30 cm) thick, and low, irregular branches. Some forms are distinctly dwarfed. The young branchlets are angular and often densely hairy, and there are usually spines on the branchlets, old limbs and trunk. Technically compound but appearing simple, having one leaflet, the leaves are alternate, ovate, ovate-oblong, or elliptic, 2 to 8 in (5-20 cm) long, 3/4 to 4 3/4 in (2-12 cm) wide, leathery, dull-green, glossy above, dull and minutely hairy beneath; the petiole broadly winged to occasionally nearly wingless. The flowers are fragrant, borne singly or in clusters of 2 to 10 in the leaf axils, or sometimes 10 to 15 in terminal racemes 4 to 12 in (10-30 cm) long; rachis and calyx hairy; the 4 to 5 petals, yellowish-white, 3/5 to 1 1/3 in (1.5-3.5 cm) long, somewhat hairy on the outside and dotted with yellow-green glands; stamens white, prominent, in bundles of 4 to 5, anthers orange. The fruit ranges from nearly round to oblate or pear-shaped; 4 to 12 in (10-30 cm) wide; the peel, clinging or more or less easily removed, may be greenish-yellow or pale-yellow, minutely hairy, dotted with tiny green glands; 1/2 to 3/4 in (1.25-2 cm) thick, the albedo soft, white or pink; pulp varies from greenish-yellow or pale-yellow to pink or red; is divided into 11 to 18 segments, very juicy to fairly dry; the segments are easily skinned and the sacs may adhere to each other or be loosely joined; the flavor varies from mildly sweet and bland to subacid or rather acid, sometimes with a faint touch of bitterness. Generally, there are only a few, large, yellowish-white seeds, white inside; though some fruits may be quite seedy. A pummelo cross-pollinated by another pummelo is apt to have numerous seeds; if cross-pollinated by sweet orange or mandarin orange, the progeny will not be seedy.
The pummelo is native to southeastern Asia and all of Malaysia; grows wild on river banks in the Fiji and Friendly Islands. It may have been introduced into China around 100 B.C. It is much cultivated in southern China (Kwang-tung, Kwangsi and Fukien Provinces) and especially in southern Thailand on the banks to the Tha Chine River; also in Taiwan and southernmost Japan, southern India, Malaya, Indonesia, New Guinea and Tahiti. The first seeds are believed to have been brought to the New World late in the 17th Century by a Captain Shaddock who stopped at Barbados on his way to England. By 1696, the fruit was being cultivated in Barbados and Jamaica. Dr. David Fairchild was enthusiastic about the first pummelo he tasted, aboard ship between Batavia and Singapore in 1899. In 1902, the United States Department of Agriculture obtained several plants from Thailand (S.P.I. Nos. 9017, 9018, 9019). Only one (No. 9017) survived and was planted in the agricultural greenhouse in Washington, and budwood from it was sent to Florida, California, Puerto Rico, Cuba (the Isle of Pines), and Trinidad. When the trees fruited, the flavor and general quality were inferior and aroused no enthusiasm. Other introductions were attempted in 1911 but all the plants died in transit. In 1913, a horticulturist of the Philippine Bureau of Agriculture was given the assignment of collecting the best types of pummelos in Thailand. He shipped to San Francisco one tree of a 'Bangkok' type that had been introduced into the Philippines in 1912; it was planted in the greenhouse of the Plant Introduction Garden at Chico. When it fruited several years later, the fruit was of such poor quality that it was considered useless. However, budwood was sent to Riverside and grafted onto two grapefruit trees growing on sour orange rootstock. One of the trees died but the other bore high-quality fruits which were much admired. Budwood was sent to different locations in Florida. In 1919, two trees of a superior pummelo (possibly 'Hao Phuang') from Thailand, which had been doing well in the Philippines, were shipped to the United States Quarantine Station in Bethesda, Maryland, and one of these survived. In addition, seeds from Thailand and from fruits in Chinese markets had been sent to Washington and seedlings were growing in greenhouses.
Dr. Fairchild was eager to introduce the red-fleshed type he had enjoyed in 1899. In 1926, he collected budwood at a hotel in Bandoeng and sent it, together with seeds, to the United States Department of Agriculture but they did not survive the trip. However, seeds of a cultivar in Kediri with flesh nearly as red as his ideal pummelo did reach the Citrus Quarantine Station in Bethesda, Maryland (as S.P.I. No. 67641), and the seedlings were grown there successfully.
In all the succeeding years, the pummelo has never attained significant status in this hemisphere. Generally, it is casually grown as a curiosity in private gardens in Florida and the Caribbean area, and mainly for experimental and breeding purposes at the United States Department of Agriculture's research stations in Orlando and Leesburg, Florida, and at Indio, California, and Mayaguez, Puerto Rico, and at the University of California's Citrus Experiment Station, Riverside. There are small commercial plantings in southern Mexico furnishing fruits for local markets. At least one fruit-grower in Lady-lake, Florida, raises pummelos on a small commercial scale. He ships the fruits to New York's Chinatown for $3 each for Chinese New Year festivities. They must be 5 in (12.5 cm) or more in diameter.
Professor G. Weidman Groff, in his Culture and Varieties of Siamese Pummelos, lists 20 named Thai cultivars, giving the date and identification number of their introduction into the United States. He describes nine. Dr. J.J. Ochse, in Fruits and Fruitculture in the Dutch East Indies, described 8 types commonly grown in Batavia. All have red or pink pulp; most have a more or less acid flavor, or a sweetish flavor with an astringent aftertaste. None seems to be of outstanding quality. Reuther, Webber and Batchelor, in Citrus Industry, Volume I, 2nd ed., describe 14 cultivars, including the best-known in Thailand, Japan, Indonesia and Tahiti and hybrids created in California. The following 22, from these and other sources, are briefly presented in alphabetical order:
'Banpeiyu' (believed to be the same as 'Pai Yau' of Taiwan)–originated in Malaya, introduced into Taiwan in 1920 and from there into Japan; nearly round, very large; peel pale-yellow, smooth, thick, tightly clinging; pulp pale-yellow, in 15-18 segments with thin but tough walls; firm but tender, juicy, of excellent, sweet-acid flavor; medium-late in season; keeps well for several months. Tree large, vigorous, with hairy new growth; leaves hairy beneath. Widely grown in the Orient; the leading cultivar of Japan where it attains high quality only in the warmest locations.
'Chandler'–a hybrid of 'Siamese Sweet' (white) and 'Siamese Pink' (acid) developed at Indio, California and released in 1961; oblate to globose; of medium size; peel smooth, at times minutely hairy, medium-thick; core small; pulp pink, fine-grained, tender, fairly juicy; segment walls thin; flavor superior to that of either parent; subacid, about 12% sugar. Seedy. Early in season; of good keeping quality.
'Daang Ai Chaa' ('Red Bantam')–grown in Thailand; round, faintly furrowed at base and apex; peel very smooth with conspicuous oil glands; the albedo sometimes tinted with pink; pulp rich-red; the segment walls thick; pulp sacs separate easily from the walls and each other; juicy; of mild flavor, neither sweet nor acid. Tree is more or less dwarfed, with low-lying branches. Non-commercial.
'Double' (incorrectly called 'Banda Navel'; known locally as 'Lemon Banda', 'Lemon Bonting', 'Lemon pompelmoes')–grown in the Banda and Ambon Islands, the Moluccas, Batavia and Java; first reported by Rumphius in 1741; sought out and found by O.A. Reinking in 1926. He supplied budwood of various types to the Departments of Agriculture in Java, Manila, and Washington, D.C. Fruit is round, oblate or faintly pear-shaped; 6 to 8 in (15-20 cm) wide; peel smooth, up to 1 in (2.5 cm) thick; shows no evidence of deformity but, inside, there is a second, rindless fruit the size of a small orange embedded in the apex. The main fruit has 19 segments, the lesser fruit 4; pulp may be red, pink-and-white, or white; is sweet and juicy; mostly seedless, rarely with one or a few more seeds. Occasionally, under adverse conditions, there are many seeds. Fruits are borne in clusters of 5 or 6; not all on a tree will be double. Tree may be low and spreading, to 15 ft (4.5 m) or upright and 18 to 30 ft (5.5-9 in) high.
'Hirado' ('Hirado Buntan')–a chance seedling found in Nagasaki Prefecture, Japan; named and introduced into cultivation around 1910; oblate; large; peel bright-yellow, smooth, glossy, medium-thick, clings tightly; pulp pale greenish-yellow, in numerous segments with thin, tough walls; tender, medium-juicy; of good, subacid flavor, faintly bitter. Medium-early in season; of good keeping quality. Tree of fairly large size, vigorous, unusually cold-tolerant. Occupies second place as a commercial cultivar in Japan.
'Hom Bai Toey' ('Scented Toey Leaf')–grown in Thailand; nearly round, slightly depressed at apex; large, 5 1/8 in (13 cm) wide; peel yellow, smooth, nearly 5/8 in (1.5 cm) thick; pulp of peculiar aroma, white, non-juicy; of slightly bitter flavor. Non-commercial.
'Kao Lang Sat' (White Lang Sat')–grown in Thailand; oval-pyriform without neck, faintly furrowed at both ends; 4 in (10 cm) wide; peel slightly rough, less than 3/8 in (1 cm) thick; pulp has peculiar aroma; pale pinkish, resembling that of the Langsat (q.v.); divided into 11 or 12 segments; sacs very dry and loosely packed; very sweet without a trace of acid; of inferior quality. Non-commercial.
'Kao Pan' ('Kao Panne', 'Khao Paen', 'White flat')–grown mainly in Nakhon Chaisri district, south of Bangkok, Thailand, for about 160 years; subglobose, flattened at base and apex; 4 1/2 in (11.5 cm) wide; peel light lemon-yellow, smooth, 3/8 to 3/4 in (1-2 cm) thick, tightly clinging; shrinks in storage; core is large and stringy; pulp is divided into 12-15 segments difficult to separate; walls are thick and tough, inedible; they are skinned off and the individual pulp sacs separate readily from each other and are eaten by the handful, like those of the pomegranate (q.v.). They are very juicy, of sweet, faintly acid flavor with hardly a hint of bitterness. Seeds under-developed and inconspicuous in June as grown locally; may be fully developed and numerous in November or when planted elsewhere. Considered the most delicious of Thai pummelos. Almost ever-bearing. Tree is round-topped and spreading, nearly thornless, very productive, but not vigorous and is subject to insects and diseases, especially prone to citrus canker. Non-commercial in Thailand. Air layers were sent to the United States Department of Agriculture's Date Garden, Indio, California, in 1929 and grown as 'Siamese Pink'. All produced seedy fruits. Trees in the United States Department of Agriculture's Foundation Farm near Leesburg, Florida, bear fruits of excellent flavor.
'Kao Phuang' ('Khao Phoang'; 'White tassel')–grown in Thailand; Groff records P.J. Wester's description of a cultivar that he named 'Siam', the budwood of which was taken by H.H. Boyle from a tree in the garden of Prince Yugelar in Bangkok, and grafted onto calamondin rootstock at the Lamao experiment station, Philippines, in 1913. The trees fruited in 1916. Reinking and Groff later determined that the Prince's tree was the 'Kao Phuang'. Fruit is elongated-pear-shaped with neck; 5 in (12.5 cm) wide or more; peel greenish to yellow, smooth, glossy, 1/2 to 3/4 in (1.25-2 cm) thick, not clinging; pulp in 11-13 segments which separate readily; walls medium thick and tough, ordinarily not eaten; pulp sacs easy to separate, very juicy; flavor excellent, somewhat acid, turning nearly sweet when fully ripe, non-bitter; seeds, few; virtually none in fruits of the third season. This is the leading and perhaps the only commercial cultivar of Thailand; in great demand; considerable quantities are exported to Hong Kong, Singapore and Malaysia. Tree is of upright habit with more thorns than 'Kao Pan'; vigorous, ever bearing, high-yielding. Thai growers maintain that this cultivar never attains the same quality when grown in other locations that it does in the Bang Bakok district. However, fruit produced at Indio, California, is of excellent quality.
'Kao Ruan Tia' ('White Dwarf')–grown in Thailand; bell-shaped; larger than 'Kao Phuang'; peel pale-yellow; pulp in as many as 16 segments; of excellent flavor; seeds numerous. Later in season than 'Kao Phuang'; non-commercial.
'Kao Yai' ('White Large')–native to the area east of the Chao Phraya River south of Bangkok; globose, symmetrical; very large, 5 1/2 in (14 cm) or more in diameter; peel light-yellow outside, slightly pinkish inside, exudes a little gum when cut, 1/2 to 3/4 in (1.25-2 cm) thick; pulp in 13 segments; sacs irregularly arranged, clinging tightly together; juicier and sweeter than 'Kao Phuang' but they become tough and indigestible if fruit is left too long on tree; seeds numerous and fully developed. Tree is upright, with a rounded top, large leaves, wavy-edged, with strongly winged petiole. Non-commercial.
'Khun Nok' ('Eagle'; 'Bang Khun Non'; 'Khun Hon Village')–closely allied to 'Kao Pan'; well suited to northern Thailand; fruit subglobose, much like 'Kao Pan'; 5 3/5 in (14.5 cm) wide; pulp of fine flavor and quality; seeds fully developed and numerous. Fruit stores and ships very well.
'Mato' ('Mato Butan'; 'Amoy')–Originated in China and introduced into Taiwan around 1700; obovoid to pear-shaped; peel pale-yellow; rough because of prominent oil glands, medium-thick, closely adhering to pulp; pulp white; segment walls thin, tough; sacs non-juicy, rather dry; flavor sweet. Early in season. The leading cultivar in Punan, China, and Taiwan; one of the three main cultivars in Japan.
'Nakhon' (mispelled 'Nakorn')–a seedling of 'Kao Pan' (PI 52388), introduced from Thailand in 1930 and grown by United States Department of Agriculture at Orlando, Florida, and at Foundation Farm at Leesburg; broad pear-shaped; small, 4 in (10 cm) wide; peel lemon-yellow; pulp white, of fine flavor. Midseason; remains in good condition for a long time on the tree.
'Pandan Bener'–grown in Java; oblate; peel smooth with small oil glands, thick but brittle; pulp dark-red; segment membranes thin but adherent; juice sacs solidly packed, less juicy than 'Pandan Wangi'; sweetish but somewhat astringent. Tree bears a moderate crop. Fruit is rarely attacked by the borer.
'Pandan Wangi'–grown in Java; oblate to round; peel rough because of large oil glands, fairly thick; pulp red, coarse-grained; segment walls thin, bitter, difficult to remove from the juice sacs which are fibrous, slightly juicy, but sweet. Tree vigorous, productive, pest-and disease-resistant but the fruits are heavily attacked by citrus rind borer.
'Reinking'–a selected seedling from a cross of 'Kao Phuang' and the 'Shamouti' orange made at Indio, California, but still a typical pummelo.
'Seeloompang'–grown in Java; pronouncedly oblate, flattened at both ends; peel green even when fully ripe, smooth, thin, brittle; pulp red; segment membranes non-adherent; juice sacs densely compacted, very juicy, acid-sweet and somewhat astringent. Very early in season.
'Siamese Sweet'–introduced by the United States Department of Agriculture in 1930 (CES 2240) and grown at the Citrus Research Center, Riverside, California; oblate to broad ovoid; pulp white, with large, crisp, non-juicy sacs easily separating from each other; mild-flavored but faintly bitter. Tree is a dwarf with drooping branches and hairy new growth.
'Tahitian' ('Moanalua'; often called 'Tahitian grapefruit')–grown from seed thought to have been taken from Borneo to Tahiti; later introduced into Hawaii; a typical pummelo but with a thin peel and amber-colored, very juicy pulp. The flavor and quality are excellent and it is locally popular.
'Thong Dee' (Khao Thongdi'; 'Golden')–grown in Thailand; oblate; large, 6 in (15 cm) wide; peel pinkish inside, 3/8 in (1 cm) thick; pulp white with light-brown streaks; pulp sacs large, separating easily from the segment walls; juicy; flavor good but inferior to that of 'Kao Pan'; seedy. Not outstanding as a shipper. Non-commercial. Tree vigorous and produces good quality fruits under unfavorable conditions. A seedling at the United States Department of Agriculture's research station in Orlando, Florida, bears fruits with pink flesh and of good quality despite having a number of seeds. In William Cooper's garden at Winter Park, a tree of this cultivar produces some seedless fruits but most are seedy. Trees at the Foundation Farm near Leesburg bear fruits of excellent flavor.
'Tresca'–a seedling from a tree in the Bahamas grew in the grove of Captain Fred Tresca in Manatee County, Florida. Discovered and propagated in 1887 by Reasoner's Nurseries, Oneco. Fruit is oblate to round, obovoid, or pear-shaped; of medium size, 4 in (10 cm) wide; peel light-yellow, smooth, thick; albedo cream-colored to white; pulp pale-orange, or pink, in 12 to 14 segments; of good flavor; very juicy; many, medium-sized seeds. Late in season. Tree of medium size; new growth hairy; very sensitive to cold. Has been grown commercially in Florida and marketed as a grapefruit. Flesh shows very little color in California.
The pummelo is tropical or near-tropical and flourishes naturally at low altitudes close to the sea. It has never performed well in New Zealand because of insufficient heat. In the prime growing region of Bang Bakok in southern Thailand, the mean temperature is 82.4º F (28º C) and mean annual rainfall is 56 in (143 cm), being heaviest from May through October and scant in January, February and March, and November and December.
It is obvious from its coastal habitat that the pummelo revels in the rich silt and sand overlying the organically enriched clay loam of the flood plain, and that it is highly tolerant of brackish water pushed inland by high tides. On the salty mud flats, farmers dig ditches and create elevated beds of soil for planting pummelo trees. They claim that salt contributes to the flavor and juiciness of the fruits. The salt content of the water varies throughout the year but may be as high as 2.11 % at times. In southern Florida and the Bahamas, the trees grow and fruit modestly on oolitic limestone. In Malaya, the tree grows well on the tailings of tin mines.
Though the seeds of the pummelo are monoembryonic, seedlings usually differ little from their parents and therefore most pummelos in the Orient are grown from seed. The seeds can be stored for 80 days at 41º F(5º C) and 56-58% relative humidity. Only the best varieties are vegetatively propagated-traditionally by air-layering but more modernly by budding onto rootstocks of pummelo, 'King' or 'Cleopatra' mandarin, rough lemon, or Rangpur lime. In experimental work in the United States, the "T", or shield-budding, method has been found most satisfactory.
Pummelo, growers in Thailand and elsewhere in southeastern Asia are primarily Chinese who dike the swampy land, dig the ditches and canals for drainage and as routes of transportation, and build the raised beds. In the 3- to 5 -year period before the beds are ready for the pummelo trees, quick crops such as bananas, sugarcane and peanuts are grown on them. Water gates at intervals along the base of the dikes, allow water to flow through hollow coconut trunks and into the ditches in the dry season. Continual deepening and widening of ditches and adding of soil to the beds is necessary to counteract erosion. Coconut and betel nut palms are planted for shade for the young citrus trees but are removed at the end of 3-5 years, or sometimes not until the pummelos are 10 to 15 years old. Rice may be grown in the ditches. The pummelo trees are spaced 10 to 15 ft (3-4.5 m) apart. Some growers interplant the colurrinar tree, Erythrina fusca Lour., to shade the mature pummelos, and to help retain the soil with its extensive, fibrous root system, and enrich the soil with its falling leaves. Weeds are removed. by hoeing. Night soil, of course, is the standard fertilizer in the Orient and is used on pummelos but, more commonly, paddy ash (the ash of burned rice hulls) is placed in piles under each tree to gradually seep down to the roots. The air-layered trees have a low, spreading habit and must eventually be pruned.
An analysis of production methods by farmers whose main source of income is marketing pummelos was made by agriculturists at the University of Malaya in 1974. It was concluded that labor input was excessive; fertilizer (all organic on mature trees), was under-utilized on young trees; chemicals were over-utilized on young trees and under-utilized on older trees which the farmers are inclined to neglect because most of them suffer from Phytophthora root rot. Pummelo trees may need nutritional sprays to correct zinc, manganese or boron deficiencies.
Harvesting and Keeping Quality
Pummelos may flower 2 to 4 times a year. In the Old World, there are usually 4 harvesting seasons. The main crop matures in November but it is said that fruits that ripen at other seasons have fewer seeds and superior quality. In Florida, the fruits ripen from November to February and there may be a small crop in the spring. In Thailand, fruits for marketing are generally picked when just beginning to turn yellow, heaped in large piles for sale. If not disposed of immediately, they are stored in dry, ventilated sheds shaded by trees. The fruits keep for long periods and ship well because of the thick peel. After 3 months, the peel will be deeply wrinkled but the pulp will be juicier and of more appealing flavor than in the fresh fruit. If stored too long, they may become bitter. Paper-wrapped fruits in ventilated crates have kept in good condition for 6 to 8 months during sea transport to Europe. According to an old Chinese Atlas, the fruits of the 'Double' pummelo, if hung in the house, will remain in good condition for a year.
Among the leading insect pests of pummelo in the Orient are a leaf miner, Phyllocnistis citrella; a flea beetle which attacks the leaves; a stinging red ant (Pheidologeton sp.) that damages roots, twigs, leaves and trunk, sometimes girdling and killing the tree. Scale insects (Chrysomphalus aonidum and C. aurantii, Coccus hesperidum, Lepidosaphes gloverii, Parlatoria brasiliensis and P. zizyphus, Pseudaonidia trilobitiformis, and Saissetia sp.) are prevalent but are partly controlled by natural enemies –a black ant (Dolochonderus sp.) and a parasitic fungus, Aschersonia aleyrodis. The weaver ant, Oecophylla smaragdina, tends scale insects for their honeydew. Fruit growers in China and Southeast Asia put out chicken entrails to encourage the weaver ant to construct its long, hanging nests on citrus trees because it controls the tree borers (Pentatomidae) and other pests. Though beneficial, it is a nuisance at harvest time because it inflicts painful stings. The "eggs" (pupae) are commonly eaten.
In Indonesia, the fruits of one cultivar, 'Bali Merah', which has a thin rind, are so heavily attacked by the citrus rind borer and other insects that they are commonly wrapped in old banana leaves, paper or cloth when young.
Sooty mold, develops on the honeydew excreted by the scale insects. The pummelo is subject to most of the diseases that affect the orange (q.v.). But Dr. Walter Swingle, on his trip to Japan, China and the Philippines, found some varieties very resistant to canker. Most of the older trees in Malaya, as already mentioned, succumb to Phytophthora root rot.
Mistletoe (Loranthus sp.) is a great pest on pummelo trees in Asia.
Though there is some labor involved, it is worth the effort to peel good pummelos, skin the segments, and eat the juicy pulp. The skinned segments can be broken apart and used in salads and desserts or made into preserves. The extracted juice is an excellent beverage. The peel can be candied.
| Food Value Per 100 g of Edible Portion* | |
| Calories | 25-58 |
| Moisture | 84.82-94.1 g |
| Protein | 0.5-0.74 g |
| Fat | 0.2-0.56 g |
| Carbohydrates | 6.3-12.4 g |
| Fiber | 0.3-0.82 g |
| Ash | 0.5-0.86 g |
| Calcium | 21-30 mg |
| Phosphorus | 20-27 mg |
| Iron | 0.3-0.5 mg |
| Vitamin A | 20 I.U. |
| Thiamine | 0.04-0.07 mg |
| Riboflavin | 0.02 mg |
| Niacin | 0.3 mg |
| Ascorbic Acid | 30-43 mg |
Like that of other citrus fruits, the peel of the pummelo contains skin irritants, mainly limonene and terpene, also citral, aldehydes, geraniol, cadinene and linalool, which may cause dermatitis in individuals having excessive contact with the oil of the outer peel. Harvesters, workers in processing factories, and housewives may develop chronic conditions on the fingers and hands.
The flowers are highly aromatic and gathered in North Vietnam for making perfume. The wood is heavy, hard, tough, fine-grained and suitable for making tool handles.
Medicinal Uses: In the Philippines and Southeast Asia, decoctions of the leaves, flowers, and rind are given for their sedative effect in cases of epilepsy, chorea and convulsive coughing. The hot leaf decoction is applied on swellings and ulcers. The fruit juice is taken as a febrifuge. The seeds are employed against coughs, dyspepsia and lumbago. Gum that exudes from declining trees is collected and taken as a cough remedy in Brazil.