SCIENTIFIC NAME: Clausena lansium

Abstract. The wampee Clausena lansium, (Lour. ) Skeels, was introduced relatively recently to Florida, and therefore is not well-known here. It is a small tree with dark green, glossy leaves and clusters of yellow spherical to oval fruits.

Propagation is easy and may be done by seed, cuttings, air layers or grafting. Superior selections have been made in the Orient but have not been introduced to Florida because of restrictions on importation of vegetative material of citrus and citrus relatives. Several selections of superior types have been made in Florida, mainly based on productivity of the tree and sweetness of the fruit. The wampee is well-adapted to the climate of southern Florida, and grows particularly well in the calcareous soils of the south-eastern coastal region. It deserves to be more widely grown for its useful fruit and for its excellent qualities as an ornamental plant.

The genus Clausena contains some 30 species and many botanical varieties distributed through the Old World Tropics (6). Of these, the wampee has the largest and most desirable fruit for human consumption. The wampee is a relative newcomer to Florida, having been introduced from China as an undetermined species in 1908 (1). It is native to southern China and Indochina. The fruit is well-known and highly esteemed in the Orient, but is little known in the American Tropics, notwithstanding the efforts of horticulturists such as David Fairchild (2). This is unfortunate because the wampee grows well in southern Florida, yields a useful fruit, and is a beautiful ornamental tree.

The plant is a large shrub or small tree reaching a height of about 20 ft (6 m) at maturity. Usually it branches near the ground and makes a multiple trunk unless specifically trained otherwise. The canopy is rounded and dense.

The leaves are pinnately compound, with 5-12 irregularly alternate leaflets 2-4 in (5-10 cm) in length. The leaflets are dark green and shiny with an undulate margin. Young branches and leaves are coarsely pubescent, becoming relatively smooth at maturity.

The greenish-white, perfect flowers are borne in large terminal panicles and the tree is self fruitful, at least in most cases. There is one crop of fruit a year in Florida. Bloom occurs from December to April, and the fruit matures from June to August. The fruit is ovoid to globose in shape and is borne in clusters which may contain 40 or more fruits (2). Fruits are 1 in (25 mm) or less in diameter and have 1-5 seeds about 0.5 in (12 mm) in length.

Seedling wampees vary in growth habit, productivity and fruit quality. Some selections have been recognized as superior to others in Florida and propagated to a limited extent. Descriptions of the great variability of wampee selections in the Orient (6) make it evident that the variability of the plants in Florida is quite limited, no doubt because they have developed from a small number of original introductions. The many superior selections of the Orient have not been brought to Florida because of quarantines against importation of vegetative propagating material of citrus species and relatives. The dangers of inadvertent spread of diseases and pests of citrus certainly justify such a quarantine. However, it is permissible to import seeds of wampee, and under the circumstances, this is the best way to broaden the genetic base of the wampee population in Florida and eventually obtain selections of better quality than those we have at present.

The wampee can be grown easily from seed and this is the most common method of propagation. The seeds are similar to citrus seeds in that they remain viable for several weeks if they are stored in a cool place and not subjected to excessive drying. Seedling plants are relatively slow-growing, but respond well to good care. They will bear fruit in 5 to 8 years usually, although under poor conditions they may take considerably longer (2).

Vegetative propagation is easily done also. Softwood cuttings can be rooted under mist. Air layers root readily during the warm months of the year. Scions of desirable selections can be grafted or budded on wampee seedlings at any time of the year. Grafting can also be done on rootstocks of some citrus species (4,6). Experiments at the University of Florida Agricultural Research and Education Center, Homestead (Campbell, C.W., Progress Reports for 1962 and 1963, Project 280, Sub-Tropical Crops of Minor Economic Importance) demonstrated that veneer grafting was much more successful than shield budding or chip budding. Grafts on rootstocks of Cleopatra mandarin (Citrus reticulata), rough lemon (C. jambhiri) and Citron (C. medica) were incompatible and died within a year after grafting. Wampee scions grafted on roostocks of shekwasha (Citrus depressa) lived for 10 years or more; however, the scions were extremely dwarfed and had other characteristics of incompatibility such as very early flowering, excessive callusing and gumming at the graft union.

Although dwarfing could be desirable, the degree of incompatibility in the wampee/citrus combinations used up to now does not show promise for the practicality of grafting wampee on citrus rootstocks. The ease with which wampee seedlings can be grown and grafted and the good compatibility with wampee scions makes wampee clearly the best choice of a rootstock at this time.

The wampee grows well in a variety of soils provided they are well-drained. It grows well in limestone soils, a feature which makes it particularly desirable in southern Dade County where such soils predominate.

Wampee trees have approximately the same cultural requirements as citrus trees and can be cared for in the same way. No disease problems have been recognized up to now, but it is possible that some could arise if large numbers of plants were grown in close proximity.

The main danger to wampee trees in Florida is cold damage. Reports of cold injury at various locations in the past make some generalizations possible (3,5). Both young and mature plants can survive air temperatures of 28-30°F without significant damage. Young plants sustain leaf and twig injury at temperatures of 26-27°F, but mature trees are usually uninjured. Large trees have extensive leaf and twig injury at 24-25°F. Trees of all ages are killed at temperatures of 20°F or below. There are records of young plants being killed in a freeze in 1934 at the Agricultural Research and Education Center, Homestead, so it is possible to have injury to wampee plants anywhere on the Florida mainland.

Such freezes occur so rarely, however, that it can be considered safe to grow the wampee anywhere in the southern coastal region of Florida. In the interior of the state it can be grown in warm sites if it can be protected from the occasional severe freezes which occur.

The fruit is most often used for fresh consumption. It has a pleasant flavor to which many people become accustomed easily. It can be used for making jellies and beverages also. Large trees will produce as much as 100 lb of fruit in a favorable year. It is not likely that commercial production of wampee will ever develop in Florida, but an enterprising grower could sell some fruit to people of Oriental origin, who know and like the fruit well enough to buy it.

The ease with which the wampee can be grown and its beauty make it a good subject for landscape use. The plant can be used very effectively as a hedge or screen, where its dense growth is particularly useful. The symmetry of the tree canopy and the color and unique texture of the foliage make it a good subject for use as a specimen plant also.

In these days of increasing emphasis on gardening and beautification of the environment, the wampee is a plant that well deserves to be more widely known and planted in the areas of Florida where it is adapted.

1. Anon. 1909. Seeds and plants imported during the period from July 1 to September 30, 1908. U.S. Dept. Agr., Bur. Plant Ind. Bul. No. 148:148.

2. Fairchild, D. 1950. The wampee, a fruit tree of the Far East. Fairchild Trop. Garden Occasional Paper No.19.

3. Ledin, R.B. 1958. Cold damage to fruit trees at the Sub-Tropical Experiment Station, Homestead, Proc. Fla. State Hort. Soc. 71:341-344.

4. Mowry, H. et al. 1958. Miscellaneous tropical and sub-tropical Florida fruits. Fla. Agr. Ext. Serv. Bul. 156A: 45-46.

5. Snow, R.E. 1963. Cold tolerance observations during the 1962 freeze. Proc. Fla. State Hort. Soc. 76:74-377.

6. Swingle, W.T., Rev. by P.C. Reece. 1967. The botany of citrus and its wild relatives. In The Citrus Industry Vol. 1, Ed. W. Reuther. University of California: 216-218.

IFAS Agricultural Research and Education Center, Homestead
Reprinted from Volume 87 of the Proceedings of the FLORIDA STATE HORTICULTURAL SOCIETY, Miami, November 5-7, 1974

DATE: November 1993

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