Growing pears in Taiwan
Growers in the lowlands graft buds onto their trees every year.
Pacific Northwest fruit growers think of Taiwan as an economic powerhouse, an ally in the Pacific Rim, and a market for fresh fruit, notably apples, cherries, pears, and stone fruit. Over the past several years, our trade relations with this country of about 23 million people have been strained due to the continuing threat of market closure resulting from quarantine concerns involving codling moth arriving in U.S. apples. Straddling the Tropic of Cancer, Taiwan is not thought of as a significant producer of deciduous tree fruit or as a location in the world that would be commercially concerned with a pest such as codling moth.
However, since the Taiwanese are among the highest per capita consumers of fresh fruit in the world, local growers seek to provide their consumers with diverse fruit choices. On an island about the size of Maryland and Delaware combined (250 miles long by 90 miles wide), Taiwanese farmers have met this challenge by producing almost 40,000 acres of apricots, plums, pears, peaches and, to a substantially lesser extent, apples. Though much of the apricot and plum crop is commercially processed, apples, peaches, and pears are prized for fresh consumption. While the level of concern for codling moth appears to be out of proportion to the risk, it is clear that Taiwan is a major subtropical producer of temperate fruits.
The few apples grown in Taiwan along with a limited amount of pears (generally Shinseiki or 20th Century) are produced at high elevations (1,500 to 2,000 meters, or 5,000 to 6,600 feet) in the central region of the island where fruit farming is promoted as a tourist attraction. Most deciduous tree fruit in Taiwan is grown in the central lowlands (below 800 meters or 2,600 feet) where farmers face a significant challenge in the lack of cold chilling temperatures.
Temperate fruit species go into rest in the fall and require a period of cold chilling to restart growth the following season. This lack of chilling is the most limiting factor in Taiwan as growers seek to produce temperate fruits in this subtropical climate. Growers and researchers in these warmer climatic areas attempt to overcome this lack-of-chilling barrier in a number of ways. In subtropical areas, temperate fruits are grown at high elevations to optimize chilling exposure; growers and local breeding programs select for varieties with low chilling requirements, and the trees are physically and chemically manipulated to shock them into reproductive synchrony.
Taiwanese fruit growers use all of these techniques to overcome the lack of chilling temperatures. However, Taiwan’s sand pear growers have added a twist that is unique to their system.
In these central lowlands, the predominant Asian pear (Pyrus serotina) is a variety called Huang-Sang, a low-chilling cultivar, considered to have inferior fruit quality compared to 20th Century. Huang-Sang pears are grown in relatively small blocks on a pergola-like trellis in which the trunk is trained upward to reach a grid of overhead wires. Any branches below the wires are removed, and fruiting branches originating above the wires are trained to a horizontal position and fastened to the trellis wire, creating a relatively complete overhead canopy about 5.5 to 6 feet above the ground.
Beginning in the 1970s, lowland pear growers began experimenting with grafting flower buds of the 20th Century cultivar onto the Huang-Sang variety. Initially, these buds were obtained from high-elevation orchards where sufficient cold chilling occurred by January or February. Credit for this innovation is given to a farmer, Mr. Jung-Sheng Son Chang, from the village of Dungshr in Taichung County, who began his experiments in 1974. These early trials showed that it was possible to produce a crop of 20th Century pears from bud grafts on the lower chilling varieties. An added benefit is that a crop of Huang-Sang pears can also be harvested from these trees, and the volume of fruit picked increases due to improved cross-pollination provided by the 20th Century flowers. By 1976, 12 local farmers had adopted the technique. Currently, of the 13,500 acres of Huang-Sang pears grown in Taiwan, 11,000 acres are grafted with buds of high-chilling pears.
During a December 2005 trip to Taiwan, I had the opportunity to visit some of these orchards, escorted by Mr. Ming-Te Lu of the Wufeng branch of the Taiwan Agricultural Research Institute and members of the management/technical staff of the Tung-Shih Farmer’s Association. We visited two different orchards of about two to three acres in size, both of which had been grafted. In this case, both orchards had been grafted with flower buds of the Hosui cultivar.
Grafting can begin as early as December, although officials recommend waiting until late January or February when the threat of colder temperature is past and the warmer temperatures increase pollination activity. Huang-Sang is a vigorous variety under Taiwan conditions, and the horizontal position of the branches gives rise to a large number of water sprouts. These sprouts are cut, leaving a 10- to 20-cm (4- to 8-inch) stub above the scaffold branch. The high-chilling flower buds are grafted onto the water sprouts using a cleft graft. Care is taken to choose a scion of similar diameter as the water sprout. The water sprout is split using a small tool called a “safety splitter” as most of the work is done at or above the grafter’s head. A short section of the dormant shoot, including a flower bud, is cut from the bud stick and carefully trimmed on opposite sides to expose the cambium layer. Following scion placement by the grafter, the graft is wrapped with red PVC tape, creating a striking visual effect. The scope of the effort in each orchard is astounding.
Huang-Sang orchards are planted at a density of about 100 trees per acre. Every tree is grafted. On 20- to 50-year-old trees, 150 to 300 buds per tree are grafted onto the water sprouts. Equally amazing is the source of the bud wood. Originally, bud wood was sourced from higher elevation areas in Taiwan, but in the operation I observed, the Hosui flower bud sticks had been imported from Japan under a permit from the Taiwanese government.
Once grafting is complete, Dormex (hydrogen cyanamide) is applied to the trees to synchronize bud break of the Huang-Sang and high-chilling variety and allow cross-pollination. Bloom occurs about 4 to 5 weeks after grafting. Estimates vary, but the Huang-Sang variety is harvested about 75 days after bloom, and the Hosui graft is harvested about 120 to 140 days after bloom, well before imported Hosui pears are available from Japan. This grafting must be done every year to maintain annual production of the high chilling variety.
In addition to grafting and the hydrogen cyanamide application, the growers are reported to carefully remove competing shoots of the high-chill cultivar, apply gibberellic acid following fruit set to hasten ripening, and to bag the fruit for cosmetic and pest control purposes. For additional information about this unique approach to pear horticulture, readers are referred to an article David Byrne and his colleague Benton Storey of Texas A&M University along with Shyi-Kuan Ou of Taiwan Agricultural Research Institute in Wufeng, published in the 1995 volume of Fruit Varieties Journal.
Risk and opportunity
How can Taiwan pear growers afford to do this? According to estimates provided by the Tung-Shih Farmer’s Association, each graft costs about U.S.$1, which covers the cost of grafting and care during the season. Each graft will produce three to four pears weighing about a kilo (2.2 pounds). Growers of the Hosui variety receive about U.S.$1 per pound. Given the large percentage of Huang-Sang pears that are grafted, this differential is apparently profitable.
Taiwan’s emergence as an industrial nation and its subsequent accession to the World Trade Organization in 2002 has created challenges for its domestic agriculture. Suitable farmland is limited; agricultural labor shortages have been chronic; and globalization and trade liberalization have allowed a growing number of cheaper agricultural imports, rendering local products less competitive. To meet WTO entry requirements, the government reduced tariffs on agricultural imports, abolished protectionist measures for some favored products, and slashed agricultural subsidies. Grafting low-chilling pears with high-chilling pears has been one innovative and successful response to those challenges for growers who are willing to take the risk.