Water Use Classification of Landscape Species (WUCOLS IV)
Water Use Classification of Landscape Species (WUCOLS IV)
Water Use Classification of Landscape Species (WUCOLS IV)
University of California
Water Use Classification of Landscape Species (WUCOLS IV)


Since substantially different climate zones exist in California, species were evaluated for regions that represent six different climatic conditions. These are not the only climate zones that exist in California, but they include much of the state where irrigated landscapes occur. For locations outside of the six regions, it is best to use species evaluations from a region that is most similar climatically to the location of interest.



Sunset climate zones*

CIMIS ET0 zones**

Representative Cities


North-Central Coastal

14, 15, 16, 17

1, 2, 3, 4, 6, 8

Healdsburg, Napa, San Jose, Salinas, San Francisco, San Luis Obispo


Central Valley

8, 9, 14

12, 14, 15, 16

Auburn, Bakersfield, Chico, Fresno, Modesto, Sacramento


South Coastal

22, 23, 24

1, 2, 4, 6

Irvine, Los Angeles, Santa Barbara, Ventura, Vista


South Inland

18, 19, 20, 21


Corona, Escondido, Pasadena, Riverside, San Bernardino, Santa Paula


High and Intermediate Desert


14, 17

Apple Valley, Barstow, Bishop, Lancaster, Lone Pine, Tehachapi


Low Desert



Borrego Springs, Blythe, Death Valley, El Centro, Needles, Palm Springs

*See Brenzel, K. N., ed., Sunset Western Garden Book (2012).

**See CIMIS ET0 Zone Map, http://wwwcimis.water.ca.gov/cimis/cimiSatEtoZones.jsp

Notes on Regions

Within each region there may be variability in climate patterns among the cities listed. For example, some cities may be considerably warmer than others during the summer months, yet they are within the same region. This variability could be reduced only by increasing the number of regions, which would enlarged the list beyond the scope of this project.

For locations considered atypical for the region, it may be useful to consider evaluations from another region that more closely characterizes the location of interest. For example, if a city in Region 1 has a climate more similar to cities in Region 2, consider Region 2 evaluations for that location. Of course, such assessments must be based on the experience and judgment of the user.

If a city is not listed and is located in California climate zone 14, for example, which overlaps Regions 1 and 2, it will be necessary to decide whether the city is more similar climatically to Petaluma (coastal influence) or the Sacramento Valley.

If a city is located in a California climate zone that is not evaluated (mainly high-elevation, cold-winter areas), a species’ water needs may be estimated by looking at all the evaluations for the species in question, then selecting the evaluation considered most appropriate. Clearly, in these cold-winter areas, hardiness is the major factor to consider.

The principal difference between the California high and intermediate desert regions is that the high desert is colder in the winter: as the elevation increases, so does the frequency of temperatures below freezing. As a result, species that are listed as appropriate for the low desert and inappropriate for the high desert may be marginally hardy and appropriate to try in the intermediate desert.





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