The kiwifruit or Chinese Gooseberry is the fruit of a large woody vine of the genus Actinidia (order Ericales, family Actinidiaceae) that grows in temperate climates. It is marketed worldwide as kiwifruit but is more commonly called kiwi in North America. The most common type of kiwifruit, Actinidia deliciosa, is about the size of a hen's egg (about 6 cm long and 4.5 to 5.5 cm around), and is often not perfectly round. It has a hairy, dull-brown skin that is not usually consumed. Inside, the flesh is bright green with rows of small, black, edible seeds. The texture of the fruit is soft and the flavour is sometimes described as a mix of strawberry, banana, and pineapple. The fruit gets its name from the short straight hairs on its skin, which closely resemble the feathers of the kiwi bird of New Zealand.
There are 94 recorded species of kiwifruit, of which the following are cultivated for their fruit:
- Actinidia deliciosa, formerly called Actinidia chinensis; by far the most common in commerce
- Actinidia chinensis, similar to Actinidia deliciosa; but with green, yellow and even yellow-red flesh
- Actinidia arguta, kokuwa, tara vine, or hardy kiwi; smaller (10-15 grams) and with green edible skins and green flesh; hardier than A. deliciosa
- Actinidia cordifolia, hardy kiwi; similar to A. arguta
- Actinidia purpurea, hardy kiwi; similar to A. arguta but red-fleshed
- Actinidia kolomikta, kolomikta, arctic beauty, or arctic kiwi; produces very small fruits, 8 grams or smaller; the hardiest species (to about -40°C)
- Actinidia polygama, silver vine; produces small fruits
Breeders have also created hybrids by deliberately crossing the preceding species.
Actinidia deliciosa is native to south-west China, and Actinidia chinensis is very common in the lower elevations of south-east China. Other species of Actinidia are also found in China and range into southeastern Siberia.
Cultivation spread from China in the early 20th century when seeds were introduced to New Zealand by Isabel Fraser, the principal of Wanganui Girls' College, who had been visiting mission schools in China. The seeds were planted in 1906 by a Wanganui nurseryman, Alexander Allison, with the vines first fruiting in 1910. People who tasted the fruit then thought it had a gooseberry flavour and began to call it the Chinese Gooseberry, but being from the actinidia family it is not related to the Grossulariaceae (gooseberry) family.
The familiar Actinidia deliciosa "Hayward" cultivar was developed by Hayward Wright in Avondale around 1924. It was initially grown in domestic gardens, but commercial planting began in the 1940s. New Zealand is now the leading producer of kiwifruit, followed by France, the United States, Italy, Spain, and Japan. Kiwifruit is still produced in its birth place in China but China has never made it to the top 10 list of kiwifruit producing countries. In China, it is grown mainly in the mountainous area upstream of Chang Jiang. It is also grown in other areas of China, including Sichuan and Taiwan.
- Macaco monkey peach (猕猴桃 Mi2 hou2 tao2): the most common name
- Unusual fruit or wonder fruit (奇異果 qi2 yi4 guo3): the most common name in Taiwan and Hong Kong (奇异果 kay yee goh). A quasi-transliteration of "kiwifruit".
- Yang peach (阳桃 Yang2 tao2)
- Goat peach (羊桃 yang2 tao2)
- Hairy pear (毛梨 mao2 li2)
- Vine pear (藤梨 teng2 li2)
The kiwifruit was called the Chinese gooseberry because of the common practice of naming a new plant after a familiar one, the gooseberry. However, New Zealand fruit-and-vegetable export company Turners and Growers began to call it the kiwifruit (after the kiwi, a flightless native bird) in 1959 to give it more marketing appeal. Growers gradually adopted the name and in 1974 the kiwifruit became the official trade name. The old name is occasionally still used in Australia.
In North America, the "fruit" part of the name is usually dropped, and most people associate "kiwi" with the fruit rather than the bird. This usage can cause some minor confusion and tends to annoy many New Zealanders. To avoid foreigners becoming confused about what a "kiwi" was: a bird, a fruit or a New Zealander, most New Zealand Kiwifruit is now marketed under the brand name Zespri (http://www.zespri.com).
Almost all kiwifruit in commerce belong to a few varieties of Actinidia deliciosa: Hayward, Chico, and Saanichton 12. The fruit of these varieties are practically indistinguishable and match the description of a standard kiwifruit given at the head of this article.
A new type of Actinidia chinensis known as "golden kiwifruit" with yellow flesh and sweet flavour resembling a tropical fruit salad was produced by New Zealand horticulturists and is being marketed worldwide in increasing volumes. Some wild vines in China have yellow fruit but are small and not commercially viable. Seeds from these plants were imported to New Zealand in 1987 and the horticulturists took eleven years to develop the new fruit through cross-pollination and grafting with green kiwi vines. Golden kiwifruit has a smooth, bronze skin, a pointed cap at one end and distinctive golden yellow flesh. It has fetched a higher market price than green kiwifruit.
Kiwifruit is a rich source of vitamin C. Its potassium content by weight is slightly less than that of a banana. It also contains vitamins A and E, calcium, iron and folic acid.
Raw kiwifruit is also rich in the protein-dissolving enzyme papain, which is commercially useful as a meat tenderizer but can be an allergen for some individuals. Specifically, people allergic to papayas or pineapples are likely to be allergic to kiwifruit also.
This enzyme, which is quickly destroyed by boiling the fruit, makes raw kiwifruit unfit for use in desserts containing milk or any other dairy products. The enzyme will start to dissolve the milk proteins within a few minutes, leaving a very unpleasant bitter taste.
Kiwifruit can be grown in most temperate climates. Where Actinidia deliciosa is not hardy, other species are grown as substitutes.
Kiwifruit is commercially grown on sturdy support structures, as it can produce several tonnes per acre, more than the rather weak vines can support. These are generally equipped with a watering system for irrigation and frost protection in the spring.
Kiwifruit vines require vigorous pruning, similar to that of grapevines. Fruit is borne on one-year-old and older canes, but declines as each cane ages. Canes should be pruned off and replaced after their third year.
Kiwifruit plants are normally dioecious, meaning that individual plants are male or female. Only female plants bear fruit, and only when pollenized by a male plant. One male pollenizer is required be planted for each three to eight female vines. An exception is the Issai variety, a hybrid (Actinidia arguta x rufa) from Japan, which produces perfect flowers and can self-pollinate; unfortunately it lacks vigour, is less hardy than most A. arguta forms and is not a large producer.
Kiwifruit is notoriously difficult to pollinate because the flowers are not very attractive to bees. Some producers blow collected pollen over the female flowers. But generally the most successful approach is saturation pollination, where the bee populations are made so large (by placing hives in the orchards) that bees are forced to use this flower because of intense competition for all flowers within flight distance.
- Purdue University NewCROP (http://www.hort.purdue.edu/newcrop/morton/kiwifruit_ars.html)
- NCBI's taxonomy browser (http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Undef&name=kiwifruit&srchmode=1&keep=1&a=Go&lvl=3) (as of August 1 2002)
- Photos of kiwifruit and alfalfa pollination in California (http://www.ellendick.com/wildbees/)