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"The first fairly complete description of this species, under the name Citrus japonica, was published in 1784 by Thunberg in his Flora japonica; it reads in translation, as follows: "petiole winged, leaves acute, shrubby stem. Japanese: Kin Kan, vulgo Fime tats banna, Kaempf., Am. ex., Fase. V. p. 801. Growing here and there, often cultivated for its little fruits. Stem shrubby, compressed-subangulate, erect, glabrous, scarcely a foot high. Branches and branchlets alternate, compressed-angular, spinose, glabrous, erect, green. Spines solitary, in the axils of the leaves, erect divergent. Leaves few, with winged petioles, ovate, somewhat acute, entire, somewhat concave, glabrous, dark green above, paler below, erect, spreading, 1 in. [2.5 cm] long, with very minute glands ('poris'). Petioles winged. 1 line [2 mm] long. Flowers axillary, often solitary, rarely paired, pediculate, nodding. Pedicels glabrous, hanging down, 1 line [2 mm] long. Parianth, 1-phyllous, green, glabrous, minute, 5-toothed. Petals 5, white, oblong, somewhat concave, spreading, somewhat claw-like. Filaments 19, subulate, compressed, erect, in 5 more or less coherent bundles, connate, forming a cylinder, shorter than the corolla, nearly equal in length, white. Anthers oblong, small, yellow. Ovary superior, subglobose, glabrous. Style solitary, cylindrical, slightly shorter than the stamens, greenish white. Stigma simple, globose, yellow, striate, many-locular within. Fruit with fleshy peel, vesicular pulp, 9-locular [sic], the size of a cherry. Differs from the other species of Citrus especially in being a very small shrub with minute fruits; thus it can scarcely be considered as a variety of orange. It resembles Citrus medica in the axillary flowers, but differs in the winged petioles; it differs from the orange in the axillary flowers, which are solitary or paired, never in panicles. Fruit ripens in December and January, is very sweet, agreeable and edible."
"This description was evidently drawn from a very small plant, perhaps an artificially dwarfed one, such as are commonly grown in Japan. The very small leaves with axillary spines, and the fruits "the size of a cherry" strongly indicate that Thunberg was describing the round kumquat and not the oval kumquat (F. margarita). His plate of this plant published in 1800 shows a flowering twig with small leaves and well-developed axillary spines.
"Hume (1903 and 1926) described this species as follows:
"'Tree similar to Nagami [F. margarita], except that it is slightly thorny, and has the leaves somewhat smaller and rounder at the apex. Leaves oval; apex obtuse; margin crenate halfway down the length; veins slightly more conspicuous than in Nagami; borne on short rigid, inconspicuously winged petioles, 1/4 to 1/2 in. [6-13 mm] in length. Fruit spherical or somewhat oblate, 1 to 1 1/4 inches [2.5-3 cm] in diameter; golden yellow, short stalked; calyx small; rind smooth, thin, spicy to the taste and aromatic when bruised; oil cells large; pulp sparse; juice acid; sections four to seven; seeds one to three, small, oval, greenish; cotyledons two, greenish. Season same as Nagami.'" (Swingle and Reece, 1967, pp 331-332)

Information compiled by TJ Siebert. (RR Krueger, 06/03/2011)

Information and nice pictures from the UC Riverside Citrus Variety Collection

Information and nice pictures from CCPP

Budded trees being grown for the variety collection by [RK Soost]. Trees in lathhouse B may be this accession and/or CRC 3789. This accession and CRC 3789 are not the same. See note dated 01/18/1989 on CRC 3789 accession card. (EM Nauer, ca 1989)

There are currently two accessions of F hindsii maintained at Riverside, PI 539723 and PI 539724. PI 539723 has traditionally been stated to be 2N and associated with the 'Golden bean' kumquat, whereas PI 539724 has been stated to be 4N and associated with the 'Hong Kong wild' kumquat. The two genotypes are compared in Swingle (1943), pp 349-353, and its revision as Swingle and Reece (1967), pp 333-335. Although Swingle (1943) has more information on these genotypes than does Swingle and Reece (1967), the later is more easily accessible (including an online version) and has most of the pertinent information. See also the information in Hodgson (1967), pp 582-583. It does appear that the received wisdom regarding the ploidy levels is probably incorrect. A letter from the late Prof RK Soost to the donor of PI 539723, Mr William Chapman, dated 07/12/1977 states "I finally have definitive chromosome counts on the F hindsi seedlings...from seed you supplied in 1975...confirming the somatic (diploid) count of 2n = 18. A separate letter from Prof Soost to the donor of PI 539724, Dr Bruce Bartholomew, states: "At long last we got some definitive chromosome counts on the Fortunella hindsii seedlings that I obtained from you in January 1978...The chromosome number of both seedlings is clearly 2n=18." Thus, it appears that both F hindsii accessions are diploid (although this should be confirmed again after over 30 years). In this case, apparently both PI 539723 and PI 539724 would correspond to Swingle's F hindsii var Chintou. In contrast to Swingle's statements in the above sources, Prof Soost states in the letter to Mr Chapman: "I suspect that the basic chromosome number...is 2n = 18, just like all other citrus and related genera...[t]he tetraploid would be the derived type...a tetraploid was either collected by chance of the tetraploid may be established as a cultivar in China. It's hard to believe that the tetraploid would be growing as a wild plant (as described by Swingle), in preference to the diploid." (RR Krueger, 12/21/2010)

CRC 3789 and 3790 compared. 3789 tree is much smaller and less vigorous growing. Leaves slightly smaller and tend to drop more readily, making small orange fruits appear more prominent. Fruits about the size of Severinia buxifolia fruits, larger on 3789 than 3790. Non-edible fruit is mostly seeds - 2 or 3 in each. (EM Nauer, 01/18/1989)

There are currently two accessions of F hindsii maintained at Riverside, PI 539723 and PI 539724. PI 539723 has traditionally been stated to be 2N and associated with the 'Golden bean' kumquat, whereas PI 539724 has been stated to be 4N and associated with the 'Hong Kong wild' kumquat. The two genotypes are compared in Swingle (1943), pp 349-353, and its revision as Swingle and Reece (1967), pp 333-335. Although Swingle (1943) has more information on these genotypes than does Swingle and Reece (1967), the later is more easily accessible (including an online version) and has most of the pertinent information. See also the information in Hodgson (1967), pp 582-583. It does appear that the received wisdom regarding the ploidy levels is probably incorrect. A letter from the late Prof RK Soost to the donor of PI 539723, Mr William Chapman, dated 07/12/1977 states "I finally have definitive chromosome counts on the F hindsi seedlings...from seed you supplied in 1975...confirming the somatic (diploid) count of 2n = 18. A separate letter from Prof Soost to the donor of PI 539724, Dr Bruce Bartholomew, states: "At long last we got some definitive chromosome counts on the Fortunella hindsii seedlings that I obtained from you in January 1978...The chromosome number of both seedlings is clearly 2n=18." Thus, it appears that both F hindsii accessions are diploid (although this should be confirmed again after over 30 years). In this case, apparently both PI 539723 and PI 539724 would correspond to Swingle's F hindsii var Chintou. In contrast to Swingle's statements in the above sources, Prof Soost states in the letter to Mr Chapman: "I suspect that the basic chromosome number...is 2n = 18, just like all other citrus and related genera...[t]he tetraploid would be the derived type...a tetraploid was either collected by chance of the tetraploid may be established as a cultivar in China. It's hard to believe that the tetraploid would be growing as a wild plant (as described by Swingle), in preference to the diploid." (RR Krueger, 12/21/2010)

Information on 'Golden Bean' kumquat from the UC Riverside Citrus Variety Collection.

"The Choju kinkan or Changshou or Fukushu kumquat of Japan is a dwarf variety that is reported to be widely grown as a potted plant in CHina and also in Japan to some extent. According to Swingle [citation below], it is characterized by the broadly obovate form of the fruit, a markedly depressed apex, medium size, thin rind (for a kumquat), and a rather large number of segments (five or six, sometimes as many as eight). Seeds are few and polyembryonic. The plant is small and thornless". (Hodgson, 1967, p 583)

Obtained from Willits and Newcomb as a possible clean source of this cv which is already in the CVC (PI 539730/RCRC 3475). More information on PI 539730 is available from the Citrus Variety Collection. Tested clean but later also processed by CCPP. (RR Krueger, 06/27/2011)

This accession was received from the US Horticultural Research Laboratory from a tree propagated from a tree formerly at the Whitmore Foundation Farm (WFF). The USHRL accession at WFF is stated in the WFF Accession Book to be "cpb-1-174 = fortunella sp plant china 1922". Another section in the Accession Book refers to "cpb 10174". The admitedly incomplete list of CPB numbers on file at NCGRCD does not show a CPB 1-174; however, it does show a CPB 10174 which is indeed stated to be "C japonica 'seedless kumquat'". The archival records also equate CPB 10174 with RCRC 2377. RCRC 2377 is an inactive accession at Riverside as of 1986. However, archival records for RCRC 2377 state: "This is not a kumquat...resembles a small mandarin." (comment by WP Bitters, ca 1969). This suggests that at some point, this accession of 'Sunki' was mislabelled as a seedless kumquat. A personal communication from Dr KD Bowman of USHRL received 07/08/2009 states: "Sunki is a small fruited mandarin that I have used in many crosses. I don't think it would be mistaken for kumquat by anyone very familiar with citrus. The oldest Sunki tree at Whitmore, 9E-2-22, is what I have used for most of my crosses. Regarding the greenhouse source of Sunki sent to you, I haven't seen it and can't offer much comment on that. The plant you indicated as the field source of the greenhouse tree, 9W-2-16, no longer exists at that location. That 9W-2-16 tree was moved to another location and appears to be typical of our 9E-2-22 Sunki at that new location. I would put more weight on the characteristics of our Sunki in the field than I would on any historical records about CPB numbers." Thus it appears that this is a legitimate accession of 'Sunki' irregardless of any documentation errors.

More information on 'Sunki' and a summary of its rootstock characteristics is available at PI 539678/RCRC 3143. (RR Krueger, 07/08/2009)