* Hong Kong, or Golden Bean kumquat (Fortunella hindsii). The most primitive kumquat type, and the only one found growing wild, in southern China. The smallest citrus fruit, grown primarily as an ornamental. Fruit pea-sized, round; rind bright red-orange, thin; pulp very scanty, bitter and acid; two to four seeds fill the fruit. Rare in the United States, not grown commercially here.
* Marumi, or round kumquat (F. japonica). Ancient Chinese kumquat type, called Luowen in China. Fruit small, round to slightly oval; rind thick, smooth, orange to yellow-orange, with prominent oil glands, intermediate between Nagami and Meiwa in sweetness; pulp can be dry or fairly juicy; one to six seeds. Commercially grown in very small quantities, prospects limited by high harvest costs.
* Meiwa, or large round kumquat (F. X crassifolia ). Jindan or Jingan in China, Neiha in Japan. Natural hybrid of Nagami and Marumi. Best kumquat for eating fresh, popular in Asia. Fruit large, slightly oval to round; rind smooth, orange, very thick and sweet; juice scanty; two to five seeds. Brought to Japan from China during the Meiwa period (1764-72), hence its name; imported to the United States 1910-12, but only recently grown commercially, on a modest scale, in California and Florida.
* Nagami, or oval kumquat (F. margarita). Ancient Chinese kumquat type, known as Luofu in China. Brought to the United States in 1850, and to California in 1880. Medium size; oval shape; rind thick, smooth, bright orange, sweet; pulp tart, fairly juicy; flavor spicy, intense, sweet-tart; two to five seeds. The standard commercial kumquat, 90% of the crop in both California and Florida.
* Nordmann Seedless kumquat (F. margarita). Discovered on a Nagami seedling by George Otto Nordmann in 1965 in DeLand, Fla. Similar to Nagami, with a slightly different shape, lighter skin and no seeds. Medium size; teardrop shape, tapered toward stem end; rind thick, yellow-orange, sweet; pulp tart, fairly juicy; flavor like Nagami; seedless. Commercially grown in very small quantities in California.
* Calamondin, or calamansi. Hybrid of kumquat and sour mandarin, or perhaps a backcross from such a hybrid to mandarin. Originated in southern China, but best known as the leading citrus fruit of the Philippines; also grown in other countries in Eastern Asia; juice used for souring, as for lime and lemon; also grown as a potted ornamental. Fruit small, round; rind smooth, deep orange, peelable when mature, edible, with kumquat flavor; pulp very tart, juicy. Recently grown commercially in California.
* Centennial variegated kumquat hybrid. Variegated mutation found on a twig of a breeding selection, a Nagami hybrid, in 1986 in Florida; grown primarily as an ornamental. Tree very attractive; fruit larger than a typical kumquat; round to oval, necked; foliage variegated gray-green, pale yellow and dark green; rind thin, sweet, striped green and yellow when young, pinkish orange against yellow-orange when mature; pulp orange, fairly acid, juicy; seedy. Trees available from nurseries.
* Eustis limequat. Hybrid of West Indian lime and Marumi kumquat made in 1909 by Walter T. Swingle, intended as a more cold-hardy lime-like fruit. Fruit larger than a kumquat, oval to round; rind very smooth, thin, light yellow, sweet and edible; pulp light green to yellow, juicy, very acid, with lime flavor; fairly seedy. Commercially grown in small quantities. Also popular as an ornamental tree.
* Fukushu, or Changshou kumquat hybrid (F. X obovata). Hybrid of kumquat and mandarin, commonly grown as a potted plant in China, and for candying fruits. Fruit large for a kumquat, slightly flattened to round; rind smooth, orange, relatively thin, sweet and edible, often peelable; pulp tart and juicy; seediness variable. Recently has been grown commercially on a modest scale in California.
* Indio mandarinquat. Hybrid of Nagami kumquat and Dancy mandarin, made at UCLA before 1972; selected in Indio. Too tart to eat fresh, but good for marmalade, and as an ornamental. Fruit larger than a kumquat, teardrop shaped, with a distinct neck; rind bright orange, rough, thin, edible but not sweet; pulp tender, juicy, tart; three to 10 seeds. Grown commercially on a small scale in California.
* Rio Grande Valley lemonquat. Discovered in Beeville, Texas, chance hybrid of a kumquat and either a Meyer lemon, or a mandarin such as Dancy or clementine (which would make it a mandarinquat). Fruits large, round; rind smooth, bright orange-yellow, sweet and edible; pulp orange-yellow, tender, very juicy, moderately tart, pleasant. Backyard favorite in Texas, trees not yet available in California.
* Tavares limequat. Hybrid of West Indian lime and Nagami kumquat made in 1909 by Swingle, intended as a more cold-hardy lime-like fruit. Fruit small, oblong, more elongated than Eustis, narrower at the stem end; rind very smooth, thin, yellow to orange-yellow, sweet and edible; pulp light green to yellow, juicy, very acid, with lime flavor; fairly seedy. Hardly grown at all in California.
* Variegated calamondin. Natural mutation of calamondin, originated with Paul Peters in Altadena, circa 1954. Attractive ornamental tree, foliage variegated dark green, light green, yellow. Fruit smaller, lighter in color when mature than calamondin, variegated, only when immature, green and yellow. Grown on a small scale by California specialty citrus farmers, to ship ornamental branches.
-- David Karp