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Ferguson, L. and M. Arpaia. 1990. New subtropical tree crops in California. p. 331-337. In: J. Janick and J.E. Simon (eds.), Advances in new crops. Timber Press, Portland, OR.

New Subtropical Tree Crops in California

Louise Ferguson and Marylu Arpaia

  6. Table 1
  7. Table 2
  8. Table 3
  9. Fig. 1


'The goal of introduction is to successfully establish a crop not previously produced in an area. Pistachios are a prime example of a recent success. They progressed from a crop of negligible value in 1976 to value of 102 million dollars in 1988 (Table 1). How this was achieved is a model of public and private sector cooperation in agricultural research and development. In contrast, Japanese persimmons, introduced at approximately the same time, have remained a small specialty crop. There are a number of other tree crops (dates, pomegranates, persimmons, feijoa, macadamias, cherimoya, mango, lychee, loquat, guava, jujube, and carob) that are struggling for a place in the California sun.

There are two aspects to successfully establishing a new crop's economic production and market development. Economically, production initially consists of locating and exploiting the proper climatic niche. If the crop proves popular, it may be adapted to less ideal climates. Production research generated by land grant universities, involves nursery production, site preparation, nutrition, irrigation, pruning, pest and disease control, harvesting, and processing. If an industry is progressive, it will fund genetic improvement as well as more fundamental research, that is of no immediate value but increases the specific knowledge of a crop. Similarly, if an industry is farsighted, legislation to offset establishment costs, and thereby encourage development of the crop, is sought.

Generally, grower associations and commodity commissions expedite the development and protection of markets. Historically, grower associations have been formed prior to a commodity commission. Commodity commissions, created by a referendum of the growers' association, are mandated by state or federal law, to levy growers for funds to support production research and market development. Growers associations are allowed to pursue legislation for tax laws favorable to industry establishment, grade standards, or tariffs to promote and protect markets.

This paper will discuss why one recent subtropical introduction, pistachios, has become a firmly established and growing industry and why another subtropical introduction of the same era, persimmons, has not. It will also review subtropical introductions to California.


Pistachio (Pistacia vera Anacardiaceae) is the only edible crop of 11 species in the genus Pistacia. The pistachio originated in Asia Minor, entered Mediterranean Europe at the beginning of the Christian era, and was introduced to California in 1890. Pistachios are deciduous and dioecious. The fruits are classified as drupes with edible seeds. They require a climate with a long, hot summer and moderate winter with at least a 1000 hours under 7.2°C (45°F). They do best in fine sandy loams but tolerate saline or alkaline soils and those with a high lime content. Though originally from a xerophytic environment, they require more water than most deciduous trees to produce well; 252 cm/ha (40 acre inches) per year under California Central Valley conditions. California's industry consists of one pistillate cultivar, 'Kerman,' a selection introduced by Dr. Whitehead in 1929 and selected by Dr. Lloyd Joley of the USDA Plant Introduction station at Chico, California, 3 staminate cultivars ('Peters', '02-16', and '02-18') and 4 rootstocks (P. terebinthus, P. atlantica, P. integerrima, and hybrid P. atlantica, P. integerrima). Seedling rootstocks are container grown, spring planted at 15 months of age and field T-budded in early summer or fall. Attempts at clonal propagation of rootstocks have been unsuccessful. Pistachios have an extended juvenility period and require 5 years of training to establish a modified central leader canopy and 7 to 10 years to reach full bearing. Physiologically the trees are characterized by embryo abortion which produces normal appearing but "blank" nuts, a failure of the shell to dehisce at harvest which produces "nonsplits," and inflorescence bud abscission which results in alternate bearing. Water relations parameters have been well developed but optimal nutritional requirements, young tree training, and mature tree pruning practices are sill under investigation. Thus far, the trees are free of viral and bacterial diseases and have geographically limited canopy fungal diseases. A single soil borne fungus, Verticillium dahliae, is a serious problem. Various insect as well as bird and rodent pest populations have, and are still, developing; some pesticide registrations have been obtained. Nematodes are not a problem.

Harvesting and processing procedures have been well developed. Aflatoxin contamination poses no problem, although the causal fungus, Aspergillus, is endemic to California soils, because all pistachios are processed within 24 hours of harvest.

There was little interest in the pistachio's potential until the 1970s. Then several factors coalesced to initiate California's pistachio industry. The first was the 1957 selection of the high quality `Kerman' cultivar. Concurrently, information generated by University of California researchers demonstrated the suitability of California's central valleys for pistachio production. Also, at this time the California aqueduct system, which irrigates the lower westside of the San Joaquin Valley, was completed. Thus, a suitable climatic niche with adequate irrigation for pistachio production was produced. Sufficient production information from University of California research and early growers trials, and potential adaptability of harvesting and processing technology from other nut crops, made pistachio production in California appear feasible. Additionally, the economic climate was favorable for developing pistachios. Due to their long juvenility, 7 to 10 years to full bearing, pistachios are expensive to develop. If a grower owns his land it costs approximately $26,400 per hectare to develop a pistachio orchard. A good grower can recoup his establishment costs in 8 years. However, the tax structure at this time allowed growers to deduct establishment costs annually. The combination of a promising cultivar, a climatic niche with adequate irrigation, production information and technology, and a favorable tax structure, made pistachio production in California possible. It was also this set of circumstances that determined the type of pistachio production that developed; because the tax structure encouraged investment in pistachios, large management corporations were formed and the major percentage of California's pistachios were developed as large plantings.

However, while the above factors made the initial establishment of pistachios in California possible, an unusual series of events made pistachios a successful introduction (Fig. 1). The single most decisive factor in the development of the California pistachio industry was the formation of The California Pistachio Association in 1976. The initial purpose of this body was to levy growers and processors for funds to support production research, locate and distribute new germplasm, and educate pistachio growers about their industry and the public about the product. Through its 12 year existence the Pistachio Commission, adhering to these purposes, in cooperation with growers and University of California, produced the successful industry that now exists.

The association initially formed a technical committee and focused its efforts and funds on production research done by the University of California in cooperation with growers. By 1978, the association formed two new committees; grades and standards, and market development. In 1981, a California Pistachio Commission, to operate in tandem with the California Pistachio Association, was formed. Through the 1980s, as crop value rose, the combined commission and association continued to support production research and increasingly supported market research and development. By 1982, funding for marketing outstripped that for production research.

The funds spent on three priorities, production research, grades and standards, and market development have produced notable economic gains for the pistachio industry. The crop research projects have addressed two issues: production problems requiring immediate field solutions, and, research that would increase the specific knowledge of the crop and improve germplasm. Earlier research tended to focus on immediate production problems, while later research has focused on more fundamental issues. Two of the most notable research gains have been in water relations and pest management. Despite their origin in a xerophytic environment, pistachios require twice as much water as originally thought to sustain good growth and produce economic crops. Production research also identified the complex of insects that produced a series of economically devastating epicarp lesions initially thought to be physiological or genetic in origin. Currently, the most pressing problems facing the pistachio industry are the devastating soil-borne fungal disease, verticillium wilt, and the physiological problems of embryo abortion, non-splitting of the shell at harvest, and the premature inflorescence bud abscission that produces alternate bearing. Current research is investigating these problems as physiological phenomena as well as focusing on new germplasm as a method of resolution.

The grades and standards, and market development committees produced the current standards to which the California industry now adheres and the product identification which the California industry initially, lacked. When California pistachios achieved economic production levels in 1976 world and domestic markets were dominated by pistachios from Iran, Syria, Turkey, and Greece (Table 2). Generally, these imported nuts are of inferior quality. The California industry set itself the goal of market recognition through a quality product. This was the origin of the California "natural pistachio," a large, naturally-split nut with an unblemished, undyed shell. This market identification was essential for development of a profitable industry.

By 1980, it became apparent that market development was to be the most important function of the pistachio commission and association. The potential production increases from new plantings, the fact that most pistachios consumed domestically were imports, and the high tariffs on exported California pistachios meant that the California industry soon would be faced with huge surpluses. The pistachio organizations prepared for this situation in two ways: first they developed an active domestic and foreign marketing campaign that promoted the California "natural pistachio;" second, they prepared for potential surpluses by seeking market protection. As early as 1980, the association funded negotiations with Japan to gradually reduce the tariff on California pistachios to 9% from a formerly non-competitive 20% against the 2% tariff on Iranian pistachios.

As an undeveloped country, Iran was granted advantages in international markets. However, an event in 1984 spurred the pistachio association to its greatest successes. In 1984, Iranian pistachio imports increased 700% over the three previous years. This rise in imports was a direct result of the Algerian Hostage Accord. In signing the U.S. agreed not to impose trade sanctions. As Iran's internal situation deteriorated and its need for foreign capital rose, U.S. importers were able to purchase Iranian pistachios under market value. Essentially, Iran was dumping pistachios in U.S. markets. Further, these frequently substandard nuts were sold under misleading labels such as "Pride of California." Therefore, not only were California pistachios being undersold but their reputation was being undermined by mislabeled imports. The commission sought relief by forming a government relations committee and focusing on unfair trade actions, compulsory country of origin labeling, and Food and Drug Administration testing of imported pistachios. In all three areas the Pistachio Commission was successful. In 1986, a 283% ad valorem duty on raw Iranian pistachios was obtained. Attempts to circumvent this with roasted product were stymied with a 318% duty. Country of origin labeling is now required. Further, testing of incoming pistachios has increased. Obviously, these legislative actions were encouraged by the political climate; Iran's hostile position and hostage taking encouraged these actions. The net effect of these actions, combined with market promotion, is a strong domestic pistachio market. Currently, the association is focusing its efforts on maintaining its high quality by attempting to control the blending of inferior hand split pistachios with naturally split product. The commission is focusing its efforts on developing foreign markets.

In summary, the pistachio has become a successful new crop in California due to fortuitous circumstances and farsighted leadership within the industry. The decades of searching, acquisition and testing by the USDA, which produced the cultivars and rootstocks, were critical factors.


Of the 400 species within the genus Diospyros, Ebenaceae, the Japanese or oriental persimmon (D. kaki L.) is one of the four, and most important commercially cultivated species. Japanese persimmons are deciduous, monecious, and set fruit parthenocarpically or with pollination. They grow well in temperate and subtropical areas tolerating both the hot, and central valleys of California as well as the more mild, humid coastal areas. They can tolerate winter temperatures of -12.2°C (10°F) but require no winter chilling. Persimmons tolerate a wide range of soils but produce best on deep, fertile, medium-textured soils with good drainage and produce better than most fruit trees on heavy clay soils. Under California San Joaquin Valley conditions they require at least 91-122 cm (36-48 inches) of irrigation in addition to winter rainfall.

Japanese persimmons originated in China but are now cultivated most extensively in Japan where they rank as the fifth most important tree fruit. Well over 500 cultivars of persimmons were introduced to the U.S. between 1870 and 1920. Of these, two major cultivars 'Hachiya' (astringent) and 'Fuyu' (non-astringent), have survived commercially. Within these classifications they are further classified as pollination constant or pollination variant. This refers to the persimmon flesh characteristic of darkening in response to seed formation. When persimmons were first introduced to this country the astringent, pollination-constant persimmon, 'Hachiya', was the more popular of the two types. The 'Hachiya' industry reached its peak in the 1940s with a total of 800 ha (2000 acres) located primarily in the central San Joaquin Valley. This has now decreased to 280 ha (700 acres) while the non-astringent, pollination-constant, 'Fuyu' increased in area. Currently, there are 600 ha (1500 acres) of 'Fuyu' persimmons in California. This industry is located in the San Joaquin Valley as well as in southwestern California.

The current 'Fuyu' cultivar situation in California is somewhat confused as could be expected because of the large number of early introductions. The four most popular "strains" are the 'Fuyu', 'California Fuyu', 'Jiro', and 'Giant' or 'Hana Fuyu'. Their differences are slight and generally not recognized in the marketplace. Trees are produced as seedling rootstocks whip or cleft grafted after a season's growth. Previously, three different rootstocks were used, D. lotus, D. kaki, and D. virginia but the first is currently most widely used. The trees are trained to a modified central leader and require 7-10 years to reach full bearing. Persimmons are relatively free of pests and diseases. The most pressing problem at this time is a decline of unknown etiology. Physiological problems include cracks radiating from the calyx, post flowering fruit drop, and alternate bearing, 'Fuyus' are selectively harvested, by color, starting in late October. The fruit is marketed with calyx intact.

When first introduced, California 'Fuyus' were sold primarily to Asians, primarily Japanese. This situation has not changed greatly. Currently, approximately half of California 'Fuyu' production is shipped to urban, instate markets primarily Los Angeles and San Francisco, and half to urban eastern markets. The major impediment to expanding 'Fuyu' production in California is lack of demand. As could be expected with such a small industry the California 'Fuyu' growers are not organized statewide; growers in the central San Joaquin Valley and those in southern California do not cooperate as an industry. Recently, a recognition of the coming surpluses by the southern California Fuyu Growers Association prompted them to initiate a state market order referendum. The initial primary objective of this order was to have been market promotion. Later objectives, included production research and cultivar identification, evaluation, and improvement. This referendum was voted on by 57% of the eligible growers and 50%, representing 35% of the 1986-87 production, were in favor of the referendum. As 51% is required, the move to establish a marketing order was defeated. It seems unlikely that the California Fuyu industry will have the impetus to expand if market development export not pursued. In lieu of a marketing order, market development will be pursued by the California Fuyu Growers Association.

Pistachios and 'Fuyu' persimmons were introduced to the Chico Plant Introduction Garden in northern California at approximately the same time. Potential climatic niches are equally available. Interest in commercial production of both peaked at the same time. Persimmons even had the advantage of a resident market, the Asian population and potential export markets, Japan and Hawaii. However, pistachios are now the third ranked nut industry in California with both domestic and export markets and persimmons are still a minor subtropical. The difference in establishment of these two subtropical introductions was how they pursued market development and protection.


California has had numerous other subtropical fruit and nut introductions over the years (Table 3). Some of these introductions have become established commercial fruit industries. The California citrus industry is the most notable example. Other introductions which are horticultural commodities include avocados (Persea americana, Lauraceae), fig (Ficus carica, Moraceae), dates (Phoenix dactylifera, Palmae) and Pomegranate (Punica granatum, Punicaceae).

Two fruit introductions which have experienced a resurgence of interest in recent years are cherimoya (Annona cherimola, Annonaceae) and feijoa (Acca selowiana, Myrtaceae). The first cherimoya trees are believed to have been planted in California in 1871. In general the tree is well adapted to southern California's coastal environments and by 1912 several cultivars had been selected and were available for commercial planting. Several small commercial enterprises were attempted at the turn of the century but failed due to low productivity and to unsuitable site selection. The lack of productivity can be overcome by hand pollination. In the late 1970s and early 1980s, the cherimoya was promoted as a new crop for northern California. Plantings which were established in the Sacramento Valley faded due to the adverse winter climate. The flurry, of activity surrounding these plantings, however, spurred the development of the small established industry now centered in southern California and the formation of the California Cherimoya Grower's Association.

As noted with the persimmon, there has been some confusion pertaining to cultivar identification. These problems are slowly being resolved by utilizing the technique of isozyme analysis. Further expansion of the industry will probably be limited due to three factors: continued urban sprawl in southern California, the high labor input required for hand pollination and limited tree adaptability to the southern California arid interior.

The feijoa was introduced into California in 1901 by Francisco Franceschi. The tree is adaptable to the diverse array of environmental conditions in California. Attempts at commercial productions were made in the 1920s but a thriving industry failed to become established although a number of named cultivars were developed. In recent years, the feijoa has been rediscovered as a potential commercial crop. This resurgence of interest was stimulated by the development of a feijoa industry in New Zealand. Based on the New Zealand industry, the California growers are planting two cultivars which were selected in the southern hemisphere, 'Mammoth' and 'Triumph'. Ironically, these two cultivars are seedling selections from material imported to New Zealand from California in the 1930s. Whether feijoas will become a successfully established fruit crop in California is unknown at this time. The California growers have organized an association which is aimed at promoting the feijoa to the consumer and sharing cultural and postharvest information. Unlike the cherimoya, whose commercial expansion is largely limited by its relative limited adaptability to California, the feijoa industry's largest challenge will be developing consumer identity and demand.

A modestly successful commercial subtropical nut crop in California is the macadamia. A member of the Proteaceae, the genus Macadamia has two species which produce edible nuts: M. integrifolia and M. tetraphylla. The California industry is based on M. tetraphylla and M. tetraphylla x integrifolia hybrids. According to the earliest records the macadamia was introduced to California in 1879 as seed material from Australia. Due to several reasons the macadamia industry in California has not developed to the extent of the Hawaiian industry which is based on M. integrifolia selections, even though there is an active growers association in California. The foremost reason is a lack of productive high quality cultivars. In Hawaii, there has been an active selection program which has sought productive high quality cultivars. Such a program has been largely lacking in California. Another limiting factor is the tree's frost sensitivity. The trees are sufficiently frost tender to limit adaptability to only the warmer coastal areas of southern California. In addition, many trees are planted as replacements for avocados which have succumbed to avocado root rot (Phyphthora cinnamomi). This has often resulted in small clusters of macadamia trees interspersed within existing avocado groves. Cultural management under these conditions is understandably difficult.

Although other subtropical fruits are grown on a limited basis in California, none have reached the level of commercial development that cherimoya, feijoa and macadamia have. These crops include passionfruit (Passiflora edulis, Passifloraceae), litchi (Litchi chinensis, Sapindaceae), loquat (Eriobotrya japonica, Rosaceae), guava (Psidium guajava, Myrtaceae), jujube (Zizyphus jujuba, Rhamnaceae) and carob (Ceratonia siliqua, Leguminosae). The carob, in particular, has had an interesting history in California. The date of its introduction into the United States is uncertain, but the records of the U.S. Patent office indicate that seed material was registered in 1854. During the 1880s, the Santa Fe Railroad planted carob trees as a landscape tree around many of its railroad stations in the southwest. In California, there was a well publicized 'Carob Crusade' spearheaded by W. Rittenhouse and J.E. Colt in the 1950s. The tree was promoted as a dryland crop needing little irrigation. Several plantings were made throughout southern California at that time. Today, however, few trees remain from these plantings. The relatively low productivity of the tree under dryland culture coupled with the high cost of processing are the major reasons the carob crusade failed. The escalating land values in southern California finked with the fact that the 1950s promotion hinged on the tax shelter benefits of the crop rather than on carob production itself also contributed to the nonviability of carob culture.

Undoubtedly, California will experience future introductions and resurgent interest in the commercial development of subtropical fruit and nut crops. Successful establishment of these commodities, however, \will hinge not only on the overall adaptability of the crop to California but whether adequate market penetration and acceptance can be achieved.


Table 1. California pistachio crop statistics, 1976-1987.

Year Acres Total production (millions of pounds) Yield/acre (lb.) Grower price/lb. ($) Total crop value (millions of dollars)
1976 4,350 1.5 344
1977 8,830 4.5 510 1.04 4.7
1978 13,150 2.5 190 1.24 3.1
1979 20,880 17.2 824 1.60 27.5
1980 25,430 26.2 1,058 2.05 55.8
1981 27,514 14.5 527 1.36 14.8
1982 28,400 43.2 1,521 1.51 65.2
1983 31,060 26.4 847 1.42 37.5
1984 30,800 62.0 2,013 0.98 61.0
1985 31,850 27.0 848 1.35 36.4
1986 32.900 74.9 2,277 1.06 79.4
1987 40,000 33.0 825 1.34 44-2
1988 44,500 91.1 2,047 1.12 102.0

Table 2. World pistachio production (1976-1990).

Production (thousands of U.S. tons)
Country 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
Iran 47.3 22.0 66.0 11.0 27.5 46.2 25.3 66.0 77.0 70.0 65.0 35.0 70.0 39.0 75.0
U.S. .6 2.2 1.2 8.6 13.6 7.3 21.7 13.2 31.5 13.5 37.5 16.0 44.0 20.0 46.0
Turkey 2.2 19.8 5.5 17.6 7.7 23.1 12.1 19.8 16.5 36.3 8.8 13.2 20.1 17.3 20.2
Syria 4.1 5.9 7.6 8.5 5.5 10.1 8.8 10.1 11.9 11.0 12.1 12.2 12.5 13.2 14.3
Greece 2.1 1.8 1.6 2.4 2.8 2.5 1.8 2.8 2.2 2.5 2.5 3.4 2.8 3.2 2.7
Italy .3 2.2 .2 5.0 .2 4.9 .2 4.4 .2 2.2 .3 4.8 .2 3.9 .2
Total 56.6 53.9 82.1 53.1 57.3 94,1 69.9 116.3 139.3 135.5 126.2 84.6 149.6 96.6 158.4

Table 3. Subtropical crops of California (1986-1987).

Crop Total hectares Total value
(U.S. $1000)
Marketing order
Commission or
Growers Assn.
All citrusz 107,354 745,226 Yes
Avocado 30,525 115,050 Yes
Pistachioy 15,854 44,317 Yes
Olives 13,619 32,170 Yes
Fig 7,363 15,651 Yes
Date 2,296 22,268 Yes
Pomegranate 1,494 4,457 No
Persimmon 496 1,532 No
Feijoa 500 Yes
Macadamia 500 No
Cherimoya 150 No
Passionfruit 25 No
Mango 50 No
Lychee 25 No
Loquat ? No
Guava ? No
Jujube ? No
Carob ? No
zDoes not include pummelos or kumquats.
yIn shell.

Fig. 1. Key events in development of California Pistachio Association and Commission and expenditures on production research and market research and development.

Last update August 28, 1997 by aw