Literature on cultivation of Eucalyptus in California suggests 188 taxa have been cultivated at various times. TJM2 treats 10 species as naturalized, whereas CCH records for 38 species are known. Calflora list 15 taxa.
About 140 other species have been used in various forestry trials at differing locations and times. There is no comprehensive account of the genus yet for FNA, and the key (Flora of Australia, Vol. 19 (1988) is difficult to use. Ritter (2012, TJM2) indicates >250 species having been cultivated in California. Ritter (2014) added a large number of cultivated records and his key is an important addition. Ritter & Yost (2009) show that many species are now fully established.
Ritter (2014) gives direct records for 137 species in California, either by his voucher or by reference to other vouchers. Ritter (2014) did not include a list of other cultivated taxa reported for California from various forestry trials as reported in Staniford & Legig (1983), King & Kurgman (1980) or Anekonda et al (1999) in his assessment, which add about 50 taxon records.
Thus, the exact number of eucalypts in California is still uncertain. Voucher specimens of all cultivated taxa are highly suggested!