TUNG
Aleurites fordii Hemsl., family EuphorbiaceaeThe tung tree has also been known as tung-nut, tung-oil, or china wood-oil tree (Fairchild 1913). The word tung is Chinese for "heart," the general shape of the leaf (Potter and Crane 1957). In 1964, there were about 7.5 million tung trees in the Southern States: Mississippi, 4.4 million; Florida, 1.7 million; Louisiana, 1.3 million; and Alabama, 0.1 million; with a few thousand in Georgia. Production of nuts amounted to 123,300 tons with a value of $7.6 million. Production amounted to only 11,700 tons valued at less than $1 million in 1970, when production estimates in USDA Agricultural Statistics were discontinued.
Tung oil, which is pressed from the nuts of this tree, is used by the protective coating industry in varnishes, enamels, and electrical insulators.
Plant:
Tung is a soft wooded, smooth-barked deciduous tree that may grow to 30 feet. First blooms appear from late February to April before the leaves appear. In bloom, the tree (fig. 187) is highly attractive because of its mass of pink blossoms similar to flowers of catalpa (Catalpa spp.). These are followed by the dense foliage of 3- to 5-inch heart-shaped dark-green leaves. Current orchard recommendations include 100 to 140 trees per acre (Potter and Crane 1957) with suggested spacings ranging from 12 by 30 feet to 15 by 40 feet. Growers allow the trees to start branching 4 to 6 feet above the ground. Tree shape is oval and symmetrical.
[gfx] FIGURE 187. Eleven-year-old tung orchard in full bloom.
Inflorescence:
The colorful and attractive blossoms (fig. 188), which are borne on the ends of the growing shoots of the previous season, vary in type. They may be all staminate, all pistillate, or predominantly one or the other (Dickey and Reuther 1940, McCann 1942). The percentage of pistillate flowers may depend on the vigor of the tree, with more such flowers produced on trees making more vigorous growth (Abbott 1929). The reddish-white flowers occur in panicled cymes or clusters with usually about 60 staminate and one pistillate flower each, with rarely a perfect flower (Newell 1924). Each flower may be an inch or more in length, and the tree is covered with the canopy of blossoms. The pistillate flowers have a three- to five-celled ovary that, when pollinated, produces a top- shaped fruit 2 to 3 inches in diameter, usually bearing five seeds. The blossoms secrete some nectar, and the staminate flowers produce a copious amount of pollen (Pering 1937)., Bees visit the blossoms freely.
[gfx] FIGURE 188. - Closeup of a flowering tung branch.
Pollination Requirements:
Angelo et al. (1942) showed that plants caged to exclude bees set no fruit and that wind or shaking the tree was of no value in fruitsetting, but when a tree was caged with a colony of honey bees a good set was obtained. Others (Hambleton 1950, Pering 1937) also credit honey bees with setting the crop. The tree is not self-sterile. It merely needs the agency to transfer the sticky pollen from the anthers of the staminate flowers to the stigma of the pistillate flower. Brown and Fisher (1941) showed that pollination can occur over several days of the life of the blossom. Webster (1943) concluded that when staminate and pistillate flowers are on separate trees, one staminate tree for 20 pistillate trees was sufficient for satisfactory pollination, provided that some staminate flowers open by the time the pistillate flowers are receptive.
Pollinators:
The pollination of tung trees is dependent upon the honey bee. Other insects visit the blossoms but rarely in sufficient abundance to be of significance. Under orchard conditions, practically every ovule of every pistillate flower is capable of developing a seed. This means that at least one viable pollen grain must land on each of the four or more lobes of the stigma of each flower at the right time to permit fertilization of the ovules. The bee population necessary to accomplish this has not been determined.
Pollination Recommendations and Practices:
No recommendations have been made on the use of bees in the pollination of tung, even though there is no doubt about their need in the production of this crop. The need for transfer of pollen grains from the staminate to all of the lobes of the pistillate flower may not require repeated visits of honey bees, but the grower should not overlook this need. To assure maximum set of nuts, he should arrange for an appropriate number of strong healthy colonies of honey bees so that every pistillate flower is well pollinated. Because of the small acreage now being grown in the United States, the demand for insect pollination is not great.
LITERATURE CITED:
ABBOTT, C. E.
1929. FRUIT BUD DEVELOPMENT IN THE TUNG OIL TREE. Jour. Agr. Res. 38: 679-696.ANGELO, E., BROWN, R. T., and AMMEN, H. J.
1942. POLLINATION STUDIES WITH TUNG TREES. Amer. Soc. Hort. Sci. Proc. 41: 176-180.BROWN, R. T., and FISHER, E.
1941. PERIOD OF STIGMA RECEPTIVITY IN FLOWERS OF TUNG TREES. Amer. Soc. Hort. Sci. Proc. 39: 164-166.DICKEY, R. D., and REUTHER, W.
1940. FLOWERING, FRUITING, YIELD AND GROWTH HABITS OF TUNG TREES. Fla. Agr. Expt. Sta. Bul. 343, 28 pp.FAIRCHILD, D.
1913. THE CHINESE WOOD-OIL TREE. U.S. Dept. Agr. Burl Plant Indus. BPI Cir. 108, 7 pp.HAMBLETON, J. I.
1950. ARE HONEY BEES NEEDED FOR THE POLLINATION OF TUNG TREES? Gleanings Bee Cult. 78: 227.MCCANN, L. P.
1942. DEVELOPMENT OF THE PISTILLATE FLOWER AND STRUCTURE OF THE FRUIT OF TUNG (ALEURITES FORDII). Jour. Agr. Res. 65: 361-378.NEWELL, W.
1924. PRELIMINARY REPORT ON EXPERIMENTS WITH THE TONG-OIL TREE IN FLORIDA. Fla. Agr. Expt. Sta. Bul. 171, pp. 193-234.PERING A. H.
1937. TUNG OIL PRODUCTION AND THE BEEKEEPER. Amer. Bee Jour. 77: 526-527.POTTER, G. F., and CRANE, H. L.
1957. TUNG PRODUCTION. U.S. Dept. Agr. Farmers' Bul. 2031, 35 pp.WEBSTER, C. C.
1943. A NOTE ON POLLINATION IN BUDDED PLANTATIONS OF TUNG TREES (ALEURITES MONTENA). Nyasaland Agr. Quart. Jour. III(3): 17-19.
