Many Shades of Orange
By Glenn I. Teves, County Extension Agent, UH CTAHR
Citrus is a family of closely related species, most of which can cross with each other to create new varieties. The main citrus species include Tachibana Orange, Lemon, Mandarin or Tangerine, Indian Wild Orange, Pummelo, Sweet Orange, Sour Orange, and Grapefruit. Grapefruit is believed to be a natural hybrid between pummelo and sweet orange discovered in the Caribbean. The Sweet Orange is among the most popular citrus, including the common or blonde orange, the sugar orange, the blood orange and the navel orange. Crosses between species have created tangelo, tangor, tantangelo, lemandarine, calamondin, and many others.
The ancestral home of citrus is widely debated and is believed to be a wide band through Southeast Asia, south of China and east of India, while others believe they originated in Australia, New Guinea, and New Caledonia. Citrus was cultivated before 300 B.C. and spread throughout Asia, Africa and the Mediterranean through conquests and trading between many civilizations, including Greeks, Romans, and Arabs, creating orchards throughout tropical Asia and Europe. Portuguese and Spanish explorers carried citrus throughout the New World, including the Americas, on their voyages of exploration and colonization, continuing the creation of new citrus varieties.
Early on, many grew citrus as a potted ornamental and medicinal plant, considering it inedible due its extremely powerful, almost medicinal fragrance which could penetrate clothes and repel attacks of noxious insects. Gradually, through the introduction of sweeter and more complex-flavored fruits, citrus attracted the attention of Europeans, who went through great expense in growing these prized fruits in special enclosed areas called orangeries. Today, we have a better understanding of these unique citrus compounds used as disinfectants and solvents, pesticides, blood thinning agents, cosmetics and perfumes, including oils as Bergamot, Petitgrain and Neroli.
Many new citrus varieties arose from the mutation of a single bud, unique and different from the parent tree. Seeds were also another important source of new varieties. Many citrus varieties are seedless when planted alone or as one variety, but will produce seeds when planted with other varieties nearby. The deep orange fruit color is enhanced by a wide difference between day and night temperatures. Some of varieties that do well in Hawaii include Washington Navel Orange, Eureka and Improved Meyer Lemon, Minneola Tangelo, Mexican and Tahitian or Bearrs Lime, Star Ruby Supreme Grapefruit, Nagami and Meiwa Kumquat, and Dancy, Clementine, Satsuma, Fremont, and Fairchild Tangerine.
With the ongoing threat of invasive pests arriving here in potted plants, we may have to rethink our methods of propagating new citrus plants on Molokai, such as grafting varieties that are already on the island, and also planting seeds and cuttings. Many varieties are grafted to special rootstocks to increase plant vigor and impart disease resistance to trees. Some citrus species produce seeds identical to their parents, such as Lime, and can be propagated from seed. One recommended method of propagating pummelo is by cuttings.
Excellent reference materials on growing citrus in Hawaii can be found at the University of Hawaii College of Tropical Agriculture and Human Resources website, ctahr.hawaii.edu/site/Info.aspx.