LITCHI OR LYCHEE (also Leechee, Lichi) Revised 1999Litchi chinensis Sonn., family Sapindaceae E. H. Erickson and A. H. Atmowidjojo

The litchi, or lychee, tree is native to southern China and southeastern Asia. It has been widely cultivated for its prized fruit since before 1766 BC and is the most important fruit plant in the Sapindaceae (Menzel, 1984). Lychee, one of the most environmentally sensitive tropical tree fruit crops, is adapted to areas of the world characterized by warm subtropics and elevated tropics having cool dry winters and warm wet summers (Menzel, 1991). China, India, Southeast Asia, and South Africa are among the major producer countries. Smaller industries exist in the United States and elsewhere (Menzel and Simpson, 1994). The fruit consists of a single seed covered by an agreeable sweet‑acid tasting, crisp, white, juicy, translucent aril or pulp, which is high in vitamin C. It may be eaten fresh, frozen, canned in syrup, or dried to produce "litchi nuts." The trees make beautiful landscape specimens with their dark green leaves and bright red fruit.

Plant:

The plant is a dense, symmetrical, oval evergreen tree with a dark brown, short, thick, trunk. Growth habit differs considerably among cultivars: Trees may have erect or drooping branches and grow 20 (6) to more than 40 feet (12 m) in height (Galan Sauco, 1989). Lychee trees can live for many years. Banta (1952) reported that two trees in China were 1,200 years old, the largest being 10.5 feet (3.2 m) in diameter. Lychee thrives in subtropical climates in acidic loamy soil with abundant moisture and well drained clay soils (Chia et. al., 1997). It will grow nearly anywhere citrus will grow, but young plants are extremely sensitive to cold and require frost protection. Mature trees can tolerate a few degrees of frost.

Commercial cultivars are geographically adapted and number over 100 world wide (Yokoyama et.al., 1991). Lychee trees are polygamous and can be propagated by seed (rarely), grafting and air layering. Air layering is most preferred because, like grafting, the trees thus produced are clones and begin to bear in from 3-5 years (Menzel, 1991). Well managed mature lychee orchards, usually about 30 trees per acre (70 trees/ha), can produce as much as 8,000-12,000 lbs of fruit per acre (10-15 tonnes of fruit/ha) in a good year. Orchards are usually planted at a much higher density and later thinned. Average yields per tree range from 22-174 lbs (10-80 kg) (Menzel, 1991). Banta (1952) reported that a 4‑year‑old tree produced 2 to 3 lbs (0.9-1.4 kg) of fruit, while a 12‑year‑old tree yielded 308 lbs (140 kg).

The round fruit, a drupe about the size of a large strawberry, is pendant in a loose cluster of several dozen fruits up to 30 in (0.76 m) long (Cobin, 1952). The leathery skin is covered with sharp‑tipped tubercles. The seeds are dark brown (Menzel, 1991). The fruit must ripen on the tree, then is harvested over a 6‑week period. The shelf life of the fresh fruit is only 10 to 14 days (Menzel, 1991, Palmer, 1956).

Inflorescence:

Lychee flowers best with days below 68^oF (20^oC) (Crane et. al., 1998, Menzel et.al., 1988, Menzel and Simpson, 1992a). The inflorescence is determinant. Small 0.08-0.12 in (2 to 3 mm), white to greenish‑yellow flowers are produced on the current season=s wood in terminal clusters (panicles), (5-30 cm) in length. They are present from mid‑February through March in the northern hemisphere (mid-August-September in the southern hemisphere). The flowers have a cup shaped calyx with 4-5 short sepals but no petals, about eight stamens, a two‑lobed stigma, an ovary on a short stalk, and one ovule in each of its two or three sections (carpels) (Galan Sauco, 1989, Menzel, 1991). Butcher (1957a) distinguished three types of flowers that bloom in stages: Male or staminate flowers (M₁) with no functional ovaries bloom first; female or functionally pistillate flowers (F) with anthers that do not dehisce comprise the second stage; and imperfect hermaphrodite flowers (M₂), also lacking functional ovaries, bloom last (see also Stern and Gazit, 1996). Each phase of bloom consists of flowers of the same type.

The onset and duration of anthesis is highly variable among cultivars (Menzel and Simpson, 1992b). Lychee flowers open throughout the day but mostly before 0600 h. Anther dehiscence occurs on day 2-5 and continues more or less throughout the day and night, but reaches its zenith around 10 a.m. The fruit bearing flowers in at least one cultivar (Mauritius) studied are normally receptive on days 2-5 following anthesis, although the bloom period may be significantly reduced when ambient temperatures are high (Stern and Gazit, 1996; Stern et.al, 1997) . The duration of flowering on a given tree is 20-45 days.

Khan (1929) cited two examples to show the floral variation on an individual panicle. On one plant, the panicle began flowering and for 10 days bore only male flowers. The next 11 days, the flowers were mixed (male or female). The remaining 6 days, only male flowers opened. Another panicle had male flowers for 13 days, mixed flowers for 2 days, all female for 2 days, mixed again for 3 days, and all male for the last 7 days. From 20 to 50 percent of all the flowers were functionally female.

A nectary occurs on every flower as a large fleshy crenulate gland within the calyx and to which the stamens and pistils are inserted. Nectar, secreted only in the morning, is highly attractive to honey bees and flies. Stern and Gazit (1996) found that nectar production was highest at 0600 h while honey bee foraging peaked in mid-morning with the F flowers being most attractive (13.3 bees/inflorescence) followed by M₂ and M₁ flowers (8.3 and 1.8 bees/inflorescence respectively) in that order. Nectar volume per flower was highest (6-29 ul) in F flowers followed by M₂ and M₁ flowers (0.3-6 and 0-1.5 ul respectively). Size of the nectary and nectar sugar concentration followed a similar pattern. There were no significant differences in sugar (fructose, glucose and sucrose) ratios among the three flower types.

Anthers dehisce longitudinally. Pollen produced by the M₂ flowers is most abundant and viable (Mustard et al. 1953). Estimated pollen viability ranges from 4-40 percent at the time of pollen release and decreases rapidly thereafter (Pivovaro, 1974). Stern and Gazit, (1996) demonstrated that the amount of pollen on individual foraging bees was two orders of magnitude greater on bees foraging on M₂ and F flowers. Corresponding pollination rates were lowest (0-20%) during the M1 and F bloom periods and highest (80-90%) with the onset of the M2 bloom. Lychee pollen seemed unattractive to wild bees in Florida (Butcher 1957a, Nakata 1956).

Fruit set occurs when pollen, primarily from M₂ flowers, is transferred to F flowers. The respective stages of bloom overlap between panicles and trees, but rarely overlap within individual panicles (Stern and Gazit, 1996). There is considerable variability in the number of F flowers per panicle (17->40%): Cultivars with the greatest number of F flowers per panicle produce the highest yields (Menzel and Simpson, 1992b). F flowers comprise 10 - 60 percent of all flowers produced depending upon the age of tree, panicle and environmental conditions (Chaturvedi, 1965).

Fruit set in lychee is climate dependent and profoundly affected by temperature and humidity. It varies greatly within panicles (McConchie and Batten, 1991), and ranges from 1-50 percent of the F flowers produced (Galan Sauco, 1989). Reproductive failure is common and not always explained. In some years, certain cultivars produce few, or only male flowers and, as a result, little or no fruit is set. This problem can be minimized through the use of better adapted varieties and management methods to retard growth and induce flowering. Winter/spring temperature extremes affecting bloom phenology and unsettled weather limiting bee flight during bloom have been identified as other causes of reproductive failure (Batten, 1986).

Pollination Requirements:

Self-pollination can occur, however, lychee F flowers are generally recognized as self-sterile and require insects, usually honey bees, to transport pollen from anthers to stigmas for fruit set (King et.al., 1989, Stern and Gazit, 1996). Chaturvedi (1965) reported 43 percent fertilized flowers on open pollinated branches, zero percent on branches bagged with muslin, and 15.5 percent on branches bagged under mosquito cloth. Das and Choudhury (1958) also reported no set of fruit on bagged panicles. Pandey and Yadava (1970) reported that only 0.03 to 0.10 percent of flowers caged to exclude insects set fruit, whereas 0.7 to 11.2 percent of flowers exposed to insect pollination set fruit. Butcher (1957a, b) also reported that no fruit set on a tree caged to exclude insect pollination. These studies clearly show that Lychee requires insect pollinators.

Lychee yields are commonly unreliable and erratic (Chia et.al, 1997, Menzel and Simpson, 1992ab, Yokoyama, et.al, 1991) and rarely approach the capacity of the tree. Degani et. al. (1995) demonstrated that abscission of fruitlets resulting from self-pollination occurs at high rates in some cultivars, resulting in high levels of hybrid fruit (76-95%) at maturity. Moreover, hybrid fruit are heavier and have larger seeds, although the latter is not necessarily desirable. Yields in rows with two cultivars adjacent to each other were 36% higher, for one cultivar, than at greater distances from the pollenizer block. There was no yield difference for a second cultivar.

Pollinators:

Honey bees are the principal pollinators of lychee (King et.al., 1989). They forage primarily between 0600 and 1200 h although foraging continues later in the day at much lower levels. Butcher (1957a, 1958) reported that in Florida the insect visitors to lychee flowers in order of numbers were: Calliphorid and screw‑worm (Callitroga[=Cochliomyia] macellaria (Fab.)) flies and honey bees. No wild bees were seen on the plant although they were present on other nearby flora. Other floral visitors include Coleoptera, Hemiptera, Homoptera and Lepidoptera (King et.al., 1989, Menzel, 1991). Pandey and Yadava (1970) reported that in India Apis spp. and Melipona spp. comprised 98 to 99 percent of the total visitors. In Thailand, A. cerana is the preferred species for small scale pollination of lychee (Wongsiri and Chen, 1995). Chaturvedi (1965) and Das and Choudhury (1958) mentioned honey bees, flies, ants, and wasps as floral visitors in India. In Australia both honey bees and Trigona sp. were found on lychee, however, preliminary studies suggest that Trigona may be too small to be effective pollinators (King et.al., 1989). Groff ( 1943) considered bees the most outstanding beneficial insects on lychee. Butcher (1957a) concluded that the value of the honey bee was obvious in the setting of lychee fruit. When lychee trees are plentiful, honey bees gather immense stores of high‑quality honey (Groff 1943; Stern and Gazit, 1996).

Pollination Recommendations and Practices:

Although no specific number of colonies per unit of lychee has been recommended, Butcher (1957a, 1958) emphasized that supplying honey bees in lychee orchards is an important and practical recommendation for assuring adequate pollination and fruit‑set. He further felt that the bees should be present continuously throughout bloom. In the absence of more definitive data, conventional wisdom derived from other orchard crop systems suggests that colonies should be provided at a minimal rate of one per acre (see also du Toit, 1990). The degree to which lychee producers provide bees for pollination is unreported.

Even though lychee cultivars may differ in their responses to cross vs. self-pollination, inter-planting will improve yields in cultivars that benefit from cross-pollination. Since there is only a partial overlapping of F and M₂ flowers within a single lychee cultivar, inter-planting of 2 or more cultivars provides optimal overlap of floral stages and ensures maximum yield potential. Moreover, abscission of fruitlets resulting from self-pollination may lead to increased percentages of hybrid fruit with higher fruit and seed weight (Stern et.al., 1993; Degani et.al., 1995).

Clearly, honey bee colonies can produce a substantial surplus honey crop in lychee stands (du Toit, 1990). Unfortunately, there is little information regarding the quality of lychee honey, the extent to which honey bees gather lychee pollen or it=s nutritive value for brood rearing. Butcher (1957a) suggests that while honey bees gather lychee pollen, lychee does not compete well with other plants as a pollen resource for honey bees. Foraging insects including honey bees may inadvertently disperse erinose mite (Eriophytes litchii) (Waite and McAlpine, 1992). Floral pests include certain caterpillars, bugs, thrips, Tortricidae, and Lycaenidae (Galan Sauco, 1989, Menzel, 1991).

LITERATURE CITED:

BANTA E. S. 1952. BEHOLD! THE LYCHEE. Amer. Fruit Grower 72(10): 10‑11, 20‑21.

BATTEN, D. J.

1986. TOWARDS AN UNDERSTANDING OF REPRODUCTIVE FAILURE IN LYCHEE (Litchi chinensis Sonn.). Acta Hort. 175:79-83.

BUTCHER, F. G. 1957a. POLLINATING INSECTS ON LYCHEE BLOSSOMS. Fla. State Hort. Soc. Proc. 70: 326‑328.

____ 1957b. BEES POLLINATE LYCHEE BLOOMS. Fla. Lychee Growers Assoc. 1956 Yearbook and Proc. 3: 59‑60.

____ 1958. POLLINATING INSECTS ON LYCHEE BLOSSOMS. Fla. Lychee Growers Assoc. 1957 Yearbook and Proc. 4: 39‑41.

CHATURVEDI, R. B. 1965. PRELIMINARY STUDIES IN THE SEX DISTRIBUTION, POLLINATION AND FRUIT DEVELOPMENT IN LITCHI (LITCHI CHINENSIS SONN.). Allahabad Farmer 39(2): 49‑51

CHIA, C. L., HAMILTON, R. A., and EVANS, D. O.

1997. LYCHEE. Univ. Hawaii C/T/A/H/R Hort. Commod. Fact Sheet #1. 4 pp.

COBIN, M. 1952. THE LYCHEE IN FLORIDA. Fruit Varieties and Hort. Digest 6: 52‑53.

CRANE, J. H., C. F. BALDERI, R. J. CAMPBELL, and R. J. KNIGHT

1998. THE LYCHEE IN FLORIDA. Univ. Fla. Coop. Ext. Serv. Fact Sheet HS-1. 8 pp.

DAS, C. S., and CHOUDHURY, R. 1958. FLORAL BIOLOGY OF LITCHI (LITCHI CHINENSIS SONN.). So. Indian Hort. 6(1): 17‑22.

DEGANI, C., STERN, R. A., EL-BATSRI, R., and GAZIT, S.

1995. POLLEN PARENT EFFECT ON THE SELECTIVE ABSCISSION OF >MAURITIUS= AND =FLORIDIAN= LYCHEE FRUITLETS. Jour. Amer. Soc. Hort. Sci. 120(3):523-526.

du Toit, A. P.

1990. POLLINATION RESEARCH: A MISSING LINK IN SUBTROPICAL FRUIT PRODUCTION. Acta Horticulturae 275, 239-243.

GALAN SAUCO, V.

1989. LITCHI CULTIVATION. Food and Agriculture Organization of the United Nations, Rome. 136 p.

GROFF, G. W.

____ 1943. SOME ECOLOGICAL FACTORS INVOLVED IN SUCCESSFUL LYCHEE CULTURE. Fla. State Hort. Soc. Proc. 56: 34‑155.

KHAN KHAN SAHEB ABDUR RAHMAN.1929. POLLINATION AND FRUIT FORMATION IN LITCHI. Agr. Jour. India 24: 183‑187.

KING, J., Exley, E. M., and VITHAGE, V.

1989. INSECT POLLINATION FOR YIELD INCREASES IN LYCHEE. Exotic Fruit Growers Assn. Proc. 4^th Austral. conf. tree nut crops. p. 142-145..

MCCONCHIE, C. A. and BATTEN, D. J.

1991. FRUIT SET IN LYCHEE (LITCHI CHINENSIS). VARIATION BETWEEN FLOWERS, PANICLES AND TREES. Aust. J. Agric. Res. 42:1163-72.

MENZEL, C. M.

1984. THE PATTERN AND CONTROL OF REPRODUCTIVE DEVELOPMENT IN LYCHEE: A REVIEW. Scientia Horticulturae. 22:333-45

MENZEL, C. M.

1991. LITCHI CHINENSIS SONN. In: Plant Resources of South-East Asia. E.W.M. Verheij and R.E. Coronel eds. Pudoc Wageningen, pp 191-195.

MENZEL, C. M., WATSON, B. J., and SIMPSON, D. R.

1988. THE LYCHEE IN AUSTRALIA. Queensland Agric. Jour. Jan.-Feb.:19-27.

MENZEL, C. M., and SIMPSON, D. R.

1992a. GROWTH, FLOWERING AND YIELD OF LYCHEE CULTIVARS. Scientia Horticulturae 49:243-254.

MENZEL, C. M., and SIMPSON, D. R.

1992b. FLOWERING AND FRUIT SET IN LYCHEE (LITCHI CHINENSIS SONN.) IN SUBTROPICAL QUEENSLAND. Aust. Jour. Exper. Agric 32:105-111.

MENZEL, C. M., and SIMPSON, D. R.

1994. LYCHEE. In: Handbook of Environmental Physiology of Fruit Crops. B. Schaffer and P.C. Andersen eds. CRC Press. vol. 2:123-145.

MUSTARD, M. J., SU‑YING, LIU, and NELSON, R. O. 1953. OBSERVATIONS OF FLORAL BIOLOGY AND FRUIT‑SETTING IN LYCHEE VARIETIES. Fla. State Hort. Soc. Proc. 66: 212 ‑ 220.

NAKATA, S. 1956. LYCHEE FLOWERING AND GIRDLING. Hawaii Farm Sci. 4(3): 4‑5.

PALMER, G. 1956. SOME ASPECTS OF THE LYCHEE AS A COMMERCIAL CROP. Fla. State Hort. Soc. Proc. 69: 308.

PANDEY, R. S., and YADAVA, R. P. S. 1970. POLLINATION OF LITCHI (LITCHI CHINENSIS) BY INSECTS WITH SPECIAL REFERENCE TO HONEYBEES. Jour. Apic. Res. 9(2): 103‑105.

PIVOVARO, S. Z.

1974. STUDIES ON THE FLORAL BIOLOGY AND THE INFLUENCE OF GROWTH REGULATORS ON FRUIT SET, SIZE AND DROP OF LITCHI CHINENSIS SONN.. M. Sc. (Agr.) Thesis, Hebrew University of Rehovot, 39 pp.

STERN, R. A., EISENSTEIN, D.VOET, H. and GAZIT, S.

1997. FEMALE >MAURITIUS= LITCHI FLOWERS ARE NOT FULLY MATURE AT ANTHESIS. Jour. Hort. Sci. 72(1):19-25.

STERN, R. A., and GAZIT, S

1996. LYCHEE POLLINATION BY THE HONEYBEE. Jour. Amer. Soc. Hort. Sci. 120(1):152-157.

STERN, R. A., GAZIT, S, EL-BATSRI, R., and DEGANI, C.

1993. POLLEN PARENT EFFECT ON OUTCROSSING RATE, YIELD, AND FRUIT CHARACTERISTICS OF FLORIDIAN AND MAURITIUS LYCHEE. Jour. Amer. Soc. Hort. Sci. 118(1):109-114.

WAITE, G. K. and MCALPINE, J. D.

1992. HONEY BEES AS CARRIERS OF LYCHEE ERINOSE MITE ERIOPHYTES LITCHII (ACARI: ERIOPHYIIDAE). Exp. Appl. Acarol., 15: 299-302.

WONGSIRI, S. and CHEN, P-P.

1995. EFFECTS OF AGRICULTURAL DEVELOPMENT ON HONEY BEES IN THAILAND. Bee World 76:3-5

YOKOYAMA, K. M., WANITPRAPHA, K., NAKAMOTO, S. T., and CHIA, C. L.

1991. LYCHEE. Univ. Hawaii C/T/A/H/R Econ. Fact Sheet #12:4 pp.