Details for: PI 539566, Citrus ×aurantium L. var. sinensis L., 'Frost Washington'

According to Soost et al (1961) (both citations), "The Frost Navel originated as a nucellar seedling obtained in 1917 by Dr HB Frost, from a Washington Nvel tree growing in the Rubidoux Tract property of the Citrus Experinment Station in Riverside. The parent tree was not especially selected for fruit quality or yield, but was one of several varieties used for a general study of juvenility and senescence in citrus. Four budded trees were planted in 1933 on the station grounds. These, and four other trees set out in 1942, have provided budwood which has been distributed to nurserymena and growers for trial since 1947."

Hodgson (1967) (pp 480-481) states that "Frost Washington is the first, and currently much the most important, nucellar budline of the Washington navel. It was originated by HB Frost, the geneticist and breeder, at the 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."

'Frost Washington' is known to decline when budded onto trifoliate rootstocks (Schneider and Pehrson, 1985). (Note: As per BIll Bitters in archival material maintained at NCGRCD, the title of the cited paper is misleading since the only navels examined were Frost nucellars). Frost Washington nucellar is less planted currently than at the time of the citations due to the availability of sanitized old line 'Washington' (maintained as PI 539360. (RR Krueger, 05/2011)

Information and nice pictures of 'Frost Washington' from the UC Riverside Citrus Variety Collection.

Information and fruit quality data from the Citrus Clonal Protection Program.