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Citrus ID


Frost Washington




Frost Navel (sec. Cottin 2002)

Cultivar or taxon


Citrus x aurantium L., pro sp. [Sweet Orange Group] (sensu Mabberley 1997, Bayer et al. 2009); Citrus sinensis (L.) Osbeck (sensu Swingle and Reece 1967; sensu Tanaka sec. Cottin 2002)



Hodgson (1967) noted that:

"Frost Washington is the first, and currently much the most important, nucellar budline of the Washington navel. It was originated by H. B. Frost, the geneticist and breeder, at the University of California Citrus Research Center, Riverside, from a controlled cross made in 1916. It was not released until 1952, however. Since that time its popularity has increased until it is now more widely planted in California, Arizona, and Morocco than any other clonal selection of Washington.

In this connection, mention should be made of the now well-established fact that Frost already has given rise through bud variation to a new and much less desirable clone, characterized by a more acid fruit of later maturity. In comparison to the Frost Washington, the fruit size and navel opening average smaller, the rind texture is coarser, and the flesh is more tender (Soost et al. 1961)."



Crown compact or dense, not weeping. First-year twig surface glabrous; second- or third-year twig surface striate; thorns absent or not persistent; prickles absent or not persistent. Petiole glabrous, length medium; wings narrow, adjoining the blade. Leaflets one, margin bluntly toothed, shade leaflet blades flat or weakly conduplicate, sun leaflet blades weakly conduplicate. Scent of crushed leaflets sweetly orange-like. Fruit as broad as long or longer than broad; rind yellow (7-10), yellow-orange (11), or orange (12); rind texture slightly rough (4-5); firmness leathery; navel present; flesh orange; taste acidic-sweet.



Bayer, R.J., D.J. Mabberley, C. Morton, C.H. Miller, I.K. Sharma, B.E. Pfeil, S. Rich, R. Hitchcock, and S. Sykes. 2009. A molecular phylogeny of the orange subfamily (Rutaceae: Aurantioideae) using nine cpDNA sequences. American Journal of Botany 96: 668–685.

Cottin, R. 2002. Citrus of the World: A citrus directory. Version 2.0. France: SRA INRA-CIRAD.

Mabberley, D.J. 1997. A classification for edible Citrus (Rutaceae). Telopea 7: 167–172.

Soost, R.K., J.W. Cameron, W.P. Bitters, and R.G. Platt. 1961. Citrus bud variation–old and new. California Citrograph 46: 176,188–93.

Swingle, W.T. and P.C. Reece. 1967. The botany of Citrus and its wild relatives. In: Reuther, W., H.J. Webber, and L.D. Batchelor (eds.). The Citrus industry. Ed. 2. Vol. I. University of California, Riverside.



Search for this cultivar in NCBI Entrez

Additional information on this cultivar at University of California: Riverside Citrus Variety Collection


Citrus ID Edition 2
October, 2011