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Other Noteworthy Citrus and Citrus Relatives

The citron (C. medica) has been grown for so long its origins are unknown, yet its fruit is almost impossible to find in this country outside of big-city specialty groceries. We know that, along with the orange, the citron was brought to Rome from Persia in the 4th century A.C.E., and despite waves of invaders, citrons were still being grown in the Hindu Kush 1200 years later. The trees reach 16 to 20 feet tall in the wild; they bear short, stout spines and green, short-petioled, virtually wingless leaves flushed purple when young. Their flowers are flushed with pink and ripen into fragrant, egg-shaped, rough and thick-rinded fruits filled with acidic or slightly sweet pale green pulp.

One variety of citron, the etrog, ethrog, esrog, or cedrat (C. medica ‘Etrog’), is the only citrus mentioned in the Bible, which gives you an idea of how long it has been appreciated. Logee’s Greenhouses, a nursery in Danielson, Connecticut, reports that etrogs can be kept at three to four feet tall in pots indoors, where they will flower year round. Their elongated fruits, which are used ritually in the ancient Jewish Feast of Tabernacles, are prized for their thick, aromatic, highly flavored, edible rinds, yellow when ripe.

Another citron, perhaps the most dramatic citrus one can grow in containers, is C. medica ‘Sarcodactylis’, the Buddha’s hand or fingered citron. Its mildly fragrant fruits sport fused, tubular, vaguely fingerlike extensions, the whole being covered with the typical thick citron rind. They are extraordinarily weird-looking, and in the East are hung in houses to perfume the air. The rind is also sliced and candied in syrup. Both of the citrons above are hardy from Zones 9-11, and both do very well as indoor subjects.

The so-called Florida orange, king mandarin, tangor, or king-of-Siam (Citrus nobilis), originally hails from Vietnam. It may be a hybrid of the tangerine with the sweet orange. It gets to around 13 feet tall in the wild, with ascending branches and spiny suckers—the flowering shoots are conveniently spineless. The thin-peeled, slightly flattened, 2- to 3-inch round fruit is yellow, flushed green to orange.

The otherwise inedible fruit of the South Italian bergamot orange (C. bergamia) has long been prized for the aromatic essential oil pressed from its skin. Its common name, “bergamot,” comes from an old Turkish term translated as “prince’s pear.” The perennial beebalm (Monarda didyma) is sometimes called bergamot, too, because the leaves of many cultivars smell like C. bergamia oil.

Tangelos and Ugli fruit (Citrus x tangelo) are of garden origin, both being hybrids of the grapefruit and the tangerine, and both possessing knobbed fruit with sweetish flesh and rough, rather loose skins. The tangelo takes after its tangerine parent, its fruit being smallish and flame-colored, particularly in the cultivar ‘Minneola’. Uglis, however, take after their grapefruit parent, their fruits being large and yellowish. In my opinion, a good tangerine beats them both hands down.

The alluringly named leech lime, Kaffir lime, or Mauritius papeda (Citrus hystrix) is a shrubby, spiny, 6- to 13-foot bush or small tree, with enlarged leaf petioles and smallish flowers. Its origins are uncertain, but it is widely naturalized throughout Southeast Asia, where it is prized for its lime-flavored leaves, and the rough rind of its small, green or yellow-flushed, 2 to 3-inch oval fruit. (Logee’s adds that the juice of the fruits is used in hair conditioners.) It can be kept confined indoors, where it blooms on and off during the year, setting fruit while still quite young. It is hardy in Zones 9-11.

One of the probable hybrids of the true lime with the sweet orange is the Rangpur lime (C. x limonia), which is also called the mandarin lime or lemandarin. It makes a medium-sized tree with spreading, hanging branches, dull green leaves, few thorns, and purple-flushed, white blossoms. It yields thin-rinded, very acidic orange fruits attractively blushed yellow or red. Some botanists classify with it the otaheite orange (C. x limonia, syn. C. otaitense), which is often found in garden centers marketed as a “mini-orange.” Very easy to grow and fruit indoors, the otaheite orange makes a small, thornless bush (the rather charming botanese word is “unarmed”), with round, 2-inch, sometimes slightly flattened, sweetish fruit that Logee’s reports can stay on the branches for years.

Kumquats are shrubby, sometimes thornless little trees with wonderfully fragrant summer flowers and bite-size, bright orange, sweet-peeled, sour-fleshed, round (or more frequently lozenge-shaped) fruits that ripen in late winter and early spring. Kumquats (the name comes from a Mandarin Chinese word meaning “golden orange”) belong to the genus Fortunella, a Chinese plant family closely related to that of Citrus. While kumquats are among the most cold-hardy of the citrus relatives, they require very warm summers to ripen their fruit.

Nonetheless, they are difficult to resist, as they are cute as all get out. ‘Nagami’ (Fortunella margarita) is a dwarf cultivar and the most commonly encountered kumquat in North America. It is hardy from Zone 8-11. A wonderful variegated sport of ‘Nagami’ is ‘Centennial’, which possesses an upright habit—pale yellow, cream, and green leaves, and fruit that starts out striped green and yellow and ripens to orange in late winter. ‘Meiwa’ (F. crassifolia) is nearly spineless, bearing rounded fruits with very thick, sweet, orange peel; it is hardy from Zones 9-11 and needs hotter summers than ‘Nagami’.

Crosses between kumquats and true citruses have resulted in xCitrofortunella (Zones 9-11), an intergeneric hybrid that has given us the limequat (xC. floridana and swinglei) and the calamondin (xC. microcarpa). This last is often marketed in garden centers as a “miniature orange,” and it is worth growing if only for its deliciously fragrant white flowers. So are its variegated forms: xC. microcarpa ‘Tiger’, which boasts green leaves streaked and edged in white, and ‘Variegata’, a compact form with white, grey, and green leaves and variegated fruits that ripen to bright orange.

Another citrus relative you’re likely to encounter as a pot plant and in gardens is the Chinese trifoliate orange (Poncitrus trifoliate, Zones 5-9). A smallish tree in the wild, its tangled, stiff green branches bristle with 3-inch spines; it has three-part, compound leaves with winged petioles, and it bears large, solitary, fragrant, waxy white, many-stamened flowers. The small 1- to 2-inch round or pear-shaped fruits are covered with a thick, rough, green to yellowish, oil-gland-dotted peel. The fruits have a pleasant scent when ripe, but their highly acidic flesh is inedible.

The trifoliate orange is one of the parents (with the sweet orange) of the citrange (xCitroncirus webberi, Zones 8-11). It is a shrubby, spreading green tree, sometimes partly deciduous, armed with vicious spines; its large, generally three-part leaves possess narrowly winged petioles. The very large, fragrant white flowers ripen to orange or yellow, 2- to 3-inch, bitter fruits.

Finally there are the real weirdos, which gardeners outside of the tropicals clubs seldom hear about. Prominent among them are the Australasian microcitruses, which botanists, always a rowdy lot, are quarreling over whether or not to reassign to the genus Citrus; the Australian round lime (Microcitrus australis); the aforementioned finger lime (Microcitrus australasica); and the xeric Australian desert lime or desert kumquat (Eremocitrus glauca). There is Clausena lansium, the wampi, much cultivated in southern China for its succulent, fuzzy, white or yellow limelike berries (there are both sweet and sour varieties). There is the Hong Kong box-orange (Severinia buxifolia), whose fruits ripen black. There’s Glycosmis pentaphylla, the so-called Jamaica mandarin orange, which hails from India and Sri Lanka, not Jamaica, and whose fruits look nothing like oranges (they are translucent white to rose-flushed globs). And there’s the white sapote (Casimiroa edulis), whose ripened yellow-green fruits offer creamy pulp with a peach custard flavor. I ate some in Key West and thought I’d died and gone to heaven.

Rand B. Lee